Payment channels: protocol tweak - when the client sends a CLOSE, the server sends a CLOSE back that contains the final negotiated contract, so it can be inserted into the wallet without needing to wait for a network broadcast (this is useful if the client does not have internet connectivity at that point).

core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClient.java

@@ -91,7 +91,9 @@ public class PaymentChannelClient {
         WAITING_FOR_INITIATE,
         WAITING_FOR_REFUND_RETURN,
         WAITING_FOR_CHANNEL_OPEN,
-        CHANNEL_OPEN
+        CHANNEL_OPEN,
+        WAITING_FOR_CHANNEL_CLOSE,
+        CHANNEL_CLOSED,
     }
     @GuardedBy("lock") private InitStep step = InitStep.WAITING_FOR_CONNECTION_OPEN;
 
@@ -253,7 +255,7 @@ public class PaymentChannelClient {
                         receiveChannelOpen();
                         return;
                     case CLOSE:
-                        conn.destroyConnection(CloseReason.SERVER_REQUESTED_CLOSE);
+                        receiveClose(msg);
                         return;
                     case ERROR:
                         checkState(msg.hasError());
@@ -290,6 +292,26 @@ public class PaymentChannelClient {
         }
     }
 
+    @GuardedBy("lock")
+    private void receiveClose(Protos.TwoWayChannelMessage msg) throws VerificationException {
+        checkState(lock.isHeldByCurrentThread());
+        if (msg.hasClose()) {
+            Transaction closeTx = new Transaction(wallet.getParams(), msg.getClose().getTx().toByteArray());
+            // TODO: set source
+            if (state != null && state().isCloseTransaction(closeTx)) {
+                // The wallet has a listener on it that the state object will use to do the right thing at this
+                // point (like watching it for confirmations). The tx has been checked by now for syntactical validity
+                // and that it correctly spends the multisig contract.
+                wallet.receivePending(closeTx, null);
+            }
+        }
+        if (step == InitStep.WAITING_FOR_CHANNEL_CLOSE)
+            conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
+        else
+            conn.destroyConnection(CloseReason.SERVER_REQUESTED_CLOSE);
+        step = InitStep.CHANNEL_CLOSED;
+    }
+
     /**
      * <p>Called when the connection terminates. Notifies the {@link StoredClientChannel} object that we can attempt to
      * resume this channel in the future and stops generating messages for the server.</p>
@@ -327,10 +349,11 @@ public class PaymentChannelClient {
         lock.lock();
         try {
             checkState(connectionOpen);
+            step = InitStep.WAITING_FOR_CHANNEL_CLOSE;
+            log.info("Sending a CLOSE message to the server and waiting for response indicating successful propagation.");
             conn.sendToServer(Protos.TwoWayChannelMessage.newBuilder()
                     .setType(Protos.TwoWayChannelMessage.MessageType.CLOSE)
                     .build());
-            conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
         } finally {
             lock.unlock();
         }

core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientState.java

@@ -123,8 +123,12 @@ public class PaymentChannelClientState {
         initWalletListeners();
     }
 
-    private boolean isCloseTransaction(Transaction tx) {
+    /**
+     * Returns true if the tx is a valid close transaction.
+     */
+    public boolean isCloseTransaction(Transaction tx) {
         try {
+            tx.verify();
             tx.getInput(0).verify(multisigContract.getOutput(0));
             return true;
         } catch (VerificationException e) {

core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServer.java

@@ -3,6 +3,8 @@ package com.google.bitcoin.protocols.channels;
 import com.google.bitcoin.core.*;
 import com.google.bitcoin.protocols.channels.PaymentChannelCloseException.CloseReason;
 import com.google.bitcoin.utils.Threading;
+import com.google.common.util.concurrent.FutureCallback;
+import com.google.common.util.concurrent.Futures;
 import com.google.protobuf.ByteString;
 import net.jcip.annotations.GuardedBy;
 import org.bitcoin.paymentchannel.Protos;
@@ -304,9 +306,31 @@ public class PaymentChannelServer {
                     case CLOSE:
                         log.info("Got CLOSE message, closing channel");
                         connectionClosing = true;
-                        if (state != null)
+                        if (state != null) {
-                            state.close();
+                            Futures.addCallback(state.close(), new FutureCallback<Transaction>() {
-                        conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
+                                @Override
+                                public void onSuccess(Transaction result) {
+                                    // Send the successfully accepted transaction back to the client.
+                                    final Protos.TwoWayChannelMessage.Builder msg = Protos.TwoWayChannelMessage.newBuilder();
+                                    msg.setType(Protos.TwoWayChannelMessage.MessageType.CLOSE);
+                                    if (result != null) {
+                                        // Result can be null on various error paths, like if we never actually opened
+                                        // properly and so on.
+                                        msg.getCloseBuilder().setTx(ByteString.copyFrom(result.bitcoinSerialize()));
+                                    }
+                                    conn.sendToClient(msg.build());
+                                    conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
+                                }
+
+                                @Override
+                                public void onFailure(Throwable t) {
+                                    log.error("Failed to broadcast close TX", t);
+                                    conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
+                                }
+                            });
+                        } else {
+                            conn.destroyConnection(CloseReason.CLIENT_REQUESTED_CLOSE);
+                        }
                         return;
                     case ERROR:
                         checkState(msg.hasError());
@@ -407,9 +431,9 @@ public class PaymentChannelServer {
         lock.lock();
         try {
             if (connectionOpen && !connectionClosing) {
-                conn.sendToClient(Protos.TwoWayChannelMessage.newBuilder()
+                final Protos.TwoWayChannelMessage.Builder msg = Protos.TwoWayChannelMessage.newBuilder();
-                        .setType(Protos.TwoWayChannelMessage.MessageType.CLOSE)
+                msg.setType(Protos.TwoWayChannelMessage.MessageType.CLOSE);
-                        .build());
+                conn.sendToClient(msg.build());
                 conn.destroyConnection(CloseReason.SERVER_REQUESTED_CLOSE);
             }
         } finally {

core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerState.java

@@ -344,7 +344,7 @@ public class PaymentChannelServerState {
         tx.getInput(0).setScriptSig(scriptSig);
     }
 
-    final SettableFuture<PaymentChannelServerState> closedFuture = SettableFuture.create();
+    final SettableFuture<Transaction> closedFuture = SettableFuture.create();
     /**
      * <p>Closes this channel and broadcasts the highest value payment transaction on the network.</p>
      *
@@ -355,11 +355,12 @@ public class PaymentChannelServerState {
      * simply set the state to {@link State#CLOSED} and let the client handle getting its refund transaction confirmed.
      * </p>
      *
-     * @return a future which completes when the provided multisig contract successfully broadcasts, or throws if the broadcast fails for some reason
+     * @return a future which completes when the provided multisig contract successfully broadcasts, or throws if the
-     *          Note that if the network simply rejects the transaction, this future will never complete, a timeout should be used.
+     *         broadcast fails for some reason. Note that if the network simply rejects the transaction, this future
-     * @throws ValueOutOfRangeException If the payment transaction would have cost more in fees to spend than it was worth
+     *         will never complete, a timeout should be used.
+     * @throws ValueOutOfRangeException If the payment tx would have cost more in fees to spend than it is worth.
      */
-    public synchronized ListenableFuture<PaymentChannelServerState> close() throws ValueOutOfRangeException {
+    public synchronized ListenableFuture<Transaction> close() throws ValueOutOfRangeException {
         if (storedServerChannel != null) {
             StoredServerChannel temp = storedServerChannel;
             storedServerChannel = null;
@@ -371,11 +372,13 @@ public class PaymentChannelServerState {
         }
 
         if (state.ordinal() < State.READY.ordinal()) {
+            log.error("Attempt to close channel in state " + state);
             state = State.CLOSED;
-            closedFuture.set(this);
+            closedFuture.set(null);
             return closedFuture;
         }
         if (state != State.READY) {
+            // TODO: What is this codepath for?
         	log.warn("Failed attempt to close a channel in state " + state);
             return closedFuture;
 		}
@@ -386,7 +389,7 @@ public class PaymentChannelServerState {
             // the submission of an initial zero-valued payment during the open phase.
 			log.warn("Closing channel that never received any payments.");
             state = State.CLOSED;
-            closedFuture.set(this);
+            closedFuture.set(null);
             return closedFuture;
         }
         Transaction tx = null;
@@ -426,7 +429,7 @@ public class PaymentChannelServerState {
             @Override public void onSuccess(Transaction transaction) {
                 log.info("TX {} propagated, channel successfully closed.", transaction.getHash());
                 state = State.CLOSED;
-                closedFuture.set(PaymentChannelServerState.this);
+                closedFuture.set(transaction);
             }
 
             @Override public void onFailure(Throwable throwable) {

core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelServerStates.java

@@ -83,7 +83,6 @@ public class StoredPaymentChannelServerStates implements WalletExtension {
         synchronized (channel) {
             channel.closeConnectedHandler();
             try {
-                //TODO add event listener to PaymentChannelServerStateManager
                 channel.getOrCreateState(wallet, broadcaster).close();
             } catch (ValueOutOfRangeException e) {
                 e.printStackTrace();

core/src/main/java/org/bitcoin/paymentchannel/Protos.java

@@ -143,6 +143,20 @@ public final class Protos {
      */
     org.bitcoin.paymentchannel.Protos.UpdatePaymentOrBuilder getUpdatePaymentOrBuilder();
 
+    // optional .paymentchannels.Close close = 9;
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    boolean hasClose();
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    org.bitcoin.paymentchannel.Protos.Close getClose();
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    org.bitcoin.paymentchannel.Protos.CloseOrBuilder getCloseOrBuilder();
+
     // optional .paymentchannels.Error error = 10;
     /**
      * <code>optional .paymentchannels.Error error = 10;</code>
@@ -316,9 +330,22 @@ public final class Protos {
               bitField0_ |= 0x00000080;
               break;
             }
+            case 74: {
+              org.bitcoin.paymentchannel.Protos.Close.Builder subBuilder = null;
+              if (((bitField0_ & 0x00000100) == 0x00000100)) {
+                subBuilder = close_.toBuilder();
+              }
+              close_ = input.readMessage(org.bitcoin.paymentchannel.Protos.Close.PARSER, extensionRegistry);
+              if (subBuilder != null) {
+                subBuilder.mergeFrom(close_);
+                close_ = subBuilder.buildPartial();
+              }
+              bitField0_ |= 0x00000100;
+              break;
+            }
             case 82: {
               org.bitcoin.paymentchannel.Protos.Error.Builder subBuilder = null;
-              if (((bitField0_ & 0x00000100) == 0x00000100)) {
+              if (((bitField0_ & 0x00000200) == 0x00000200)) {
                 subBuilder = error_.toBuilder();
               }
               error_ = input.readMessage(org.bitcoin.paymentchannel.Protos.Error.PARSER, extensionRegistry);
@@ -326,7 +353,7 @@ public final class Protos {
                 subBuilder.mergeFrom(error_);
                 error_ = subBuilder.buildPartial();
               }
-              bitField0_ |= 0x00000100;
+              bitField0_ |= 0x00000200;
               break;
             }
           }
@@ -419,10 +446,15 @@ public final class Protos {
        * <code>CLOSE = 9;</code>
        *
        * <pre>
-       * Note that there are no optional fields set for CLOSE, it is sent by either party to
+       * Either side can send this message. If the client sends it to the server, then the server
-       * indicate that the channel is now closed and no further updates can happen. After this,
+       * takes the most recent signature it received in an UPDATE_PAYMENT and uses it to create a
-       * the secondary takes the most recent signature it received in an UPDATE_PAYMENT and
+       * valid transaction, which it then broadcasts on the network.
-       * uses it to create a valid transaction, which it then broadcasts on the network.
+       *
+       * If the server sends it to the client, then it can either be a simple "good bye" message or
+       * it can include the fully signed close transaction and give it back so the client can
+       * eventually broadcast it as well, in case the server fails to do so for some reason (and
+       * more usefully so the client can build on it). In that case the server replies to a CLOSE
+       * with another CLOSE and then disconnects.
        * </pre>
        */
       CLOSE(8, 9),
@@ -432,7 +464,8 @@ public final class Protos {
        * <pre>
        * Used to indicate an error condition.
        * Both parties should make an effort to send either an ERROR or a CLOSE immediately
-       * before closing the socket (unless they just received an ERROR or a CLOSE)
+       * before closing the socket (unless they just received an ERROR or a CLOSE). This is important
+       * because the protocol may not run over TCP.
        * </pre>
        */
       ERROR(9, 10),
@@ -484,10 +517,15 @@ public final class Protos {
        * <code>CLOSE = 9;</code>
        *
        * <pre>
-       * Note that there are no optional fields set for CLOSE, it is sent by either party to
+       * Either side can send this message. If the client sends it to the server, then the server
-       * indicate that the channel is now closed and no further updates can happen. After this,
+       * takes the most recent signature it received in an UPDATE_PAYMENT and uses it to create a
-       * the secondary takes the most recent signature it received in an UPDATE_PAYMENT and
+       * valid transaction, which it then broadcasts on the network.
-       * uses it to create a valid transaction, which it then broadcasts on the network.
+       *
+       * If the server sends it to the client, then it can either be a simple "good bye" message or
+       * it can include the fully signed close transaction and give it back so the client can
+       * eventually broadcast it as well, in case the server fails to do so for some reason (and
+       * more usefully so the client can build on it). In that case the server replies to a CLOSE
+       * with another CLOSE and then disconnects.
        * </pre>
        */
       public static final int CLOSE_VALUE = 9;
@@ -497,7 +535,8 @@ public final class Protos {
        * <pre>
        * Used to indicate an error condition.
        * Both parties should make an effort to send either an ERROR or a CLOSE immediately
-       * before closing the socket (unless they just received an ERROR or a CLOSE)
+       * before closing the socket (unless they just received an ERROR or a CLOSE). This is important
+       * because the protocol may not run over TCP.
        * </pre>
        */
       public static final int ERROR_VALUE = 10;
@@ -763,6 +802,28 @@ public final class Protos {
       return updatePayment_;
     }
 
+    // optional .paymentchannels.Close close = 9;
+    public static final int CLOSE_FIELD_NUMBER = 9;
+    private org.bitcoin.paymentchannel.Protos.Close close_;
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    public boolean hasClose() {
+      return ((bitField0_ & 0x00000100) == 0x00000100);
+    }
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    public org.bitcoin.paymentchannel.Protos.Close getClose() {
+      return close_;
+    }
+    /**
+     * <code>optional .paymentchannels.Close close = 9;</code>
+     */
+    public org.bitcoin.paymentchannel.Protos.CloseOrBuilder getCloseOrBuilder() {
+      return close_;
+    }
+
     // optional .paymentchannels.Error error = 10;
     public static final int ERROR_FIELD_NUMBER = 10;
     private org.bitcoin.paymentchannel.Protos.Error error_;
@@ -770,7 +831,7 @@ public final class Protos {
      * <code>optional .paymentchannels.Error error = 10;</code>
      */
     public boolean hasError() {
-      return ((bitField0_ & 0x00000100) == 0x00000100);
+      return ((bitField0_ & 0x00000200) == 0x00000200);
     }
     /**
      * <code>optional .paymentchannels.Error error = 10;</code>
@@ -794,6 +855,7 @@ public final class Protos {
       returnRefund_ = org.bitcoin.paymentchannel.Protos.ReturnRefund.getDefaultInstance();
       provideContract_ = org.bitcoin.paymentchannel.Protos.ProvideContract.getDefaultInstance();
       updatePayment_ = org.bitcoin.paymentchannel.Protos.UpdatePayment.getDefaultInstance();
+      close_ = org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance();
       error_ = org.bitcoin.paymentchannel.Protos.Error.getDefaultInstance();
     }
     private byte memoizedIsInitialized = -1;
@@ -847,6 +909,12 @@ public final class Protos {
           return false;
         }
       }
+      if (hasClose()) {
+        if (!getClose().isInitialized()) {
+          memoizedIsInitialized = 0;
+          return false;
+        }
+      }
       memoizedIsInitialized = 1;
       return true;
     }
@@ -879,6 +947,9 @@ public final class Protos {
         output.writeMessage(8, updatePayment_);
       }
       if (((bitField0_ & 0x00000100) == 0x00000100)) {
+        output.writeMessage(9, close_);
+      }
+      if (((bitField0_ & 0x00000200) == 0x00000200)) {
         output.writeMessage(10, error_);
       }
       getUnknownFields().writeTo(output);
@@ -923,6 +994,10 @@ public final class Protos {
           .computeMessageSize(8, updatePayment_);
       }
       if (((bitField0_ & 0x00000100) == 0x00000100)) {
+        size += com.google.protobuf.CodedOutputStream
+          .computeMessageSize(9, close_);
+      }
+      if (((bitField0_ & 0x00000200) == 0x00000200)) {
         size += com.google.protobuf.CodedOutputStream
           .computeMessageSize(10, error_);
       }
@@ -1047,6 +1122,7 @@ public final class Protos {
           getReturnRefundFieldBuilder();
           getProvideContractFieldBuilder();
           getUpdatePaymentFieldBuilder();
+          getCloseFieldBuilder();
           getErrorFieldBuilder();
         }
       }
@@ -1100,12 +1176,18 @@ public final class Protos {
           updatePaymentBuilder_.clear();
         }
         bitField0_ = (bitField0_ & ~0x00000080);
+        if (closeBuilder_ == null) {
+          close_ = org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance();
+        } else {
+          closeBuilder_.clear();
+        }
+        bitField0_ = (bitField0_ & ~0x00000100);
         if (errorBuilder_ == null) {
           error_ = org.bitcoin.paymentchannel.Protos.Error.getDefaultInstance();
         } else {
           errorBuilder_.clear();
         }
-        bitField0_ = (bitField0_ & ~0x00000100);
+        bitField0_ = (bitField0_ & ~0x00000200);
         return this;
       }
 
@@ -1197,6 +1279,14 @@ public final class Protos {
         if (((from_bitField0_ & 0x00000100) == 0x00000100)) {
           to_bitField0_ |= 0x00000100;
         }
+        if (closeBuilder_ == null) {
+          result.close_ = close_;
+        } else {
+          result.close_ = closeBuilder_.build();
+        }
+        if (((from_bitField0_ & 0x00000200) == 0x00000200)) {
+          to_bitField0_ |= 0x00000200;
+        }
         if (errorBuilder_ == null) {
           result.error_ = error_;
         } else {
@@ -1242,6 +1332,9 @@ public final class Protos {
         if (other.hasUpdatePayment()) {
           mergeUpdatePayment(other.getUpdatePayment());
         }
+        if (other.hasClose()) {
+          mergeClose(other.getClose());
+        }
         if (other.hasError()) {
           mergeError(other.getError());
         }
@@ -1296,6 +1389,12 @@ public final class Protos {
             return false;
           }
         }
+        if (hasClose()) {
+          if (!getClose().isInitialized()) {
+            
+            return false;
+          }
+        }
         return true;
       }
 
@@ -2233,6 +2332,123 @@ public final class Protos {
         return updatePaymentBuilder_;
       }
 
+      // optional .paymentchannels.Close close = 9;
+      private org.bitcoin.paymentchannel.Protos.Close close_ = org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance();
+      private com.google.protobuf.SingleFieldBuilder<
+          org.bitcoin.paymentchannel.Protos.Close, org.bitcoin.paymentchannel.Protos.Close.Builder, org.bitcoin.paymentchannel.Protos.CloseOrBuilder> closeBuilder_;
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public boolean hasClose() {
+        return ((bitField0_ & 0x00000100) == 0x00000100);
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public org.bitcoin.paymentchannel.Protos.Close getClose() {
+        if (closeBuilder_ == null) {
+          return close_;
+        } else {
+          return closeBuilder_.getMessage();
+        }
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public Builder setClose(org.bitcoin.paymentchannel.Protos.Close value) {
+        if (closeBuilder_ == null) {
+          if (value == null) {
+            throw new NullPointerException();
+          }
+          close_ = value;
+          onChanged();
+        } else {
+          closeBuilder_.setMessage(value);
+        }
+        bitField0_ |= 0x00000100;
+        return this;
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public Builder setClose(
+          org.bitcoin.paymentchannel.Protos.Close.Builder builderForValue) {
+        if (closeBuilder_ == null) {
+          close_ = builderForValue.build();
+          onChanged();
+        } else {
+          closeBuilder_.setMessage(builderForValue.build());
+        }
+        bitField0_ |= 0x00000100;
+        return this;
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public Builder mergeClose(org.bitcoin.paymentchannel.Protos.Close value) {
+        if (closeBuilder_ == null) {
+          if (((bitField0_ & 0x00000100) == 0x00000100) &&
+              close_ != org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance()) {
+            close_ =
+              org.bitcoin.paymentchannel.Protos.Close.newBuilder(close_).mergeFrom(value).buildPartial();
+          } else {
+            close_ = value;
+          }
+          onChanged();
+        } else {
+          closeBuilder_.mergeFrom(value);
+        }
+        bitField0_ |= 0x00000100;
+        return this;
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public Builder clearClose() {
+        if (closeBuilder_ == null) {
+          close_ = org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance();
+          onChanged();
+        } else {
+          closeBuilder_.clear();
+        }
+        bitField0_ = (bitField0_ & ~0x00000100);
+        return this;
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public org.bitcoin.paymentchannel.Protos.Close.Builder getCloseBuilder() {
+        bitField0_ |= 0x00000100;
+        onChanged();
+        return getCloseFieldBuilder().getBuilder();
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      public org.bitcoin.paymentchannel.Protos.CloseOrBuilder getCloseOrBuilder() {
+        if (closeBuilder_ != null) {
+          return closeBuilder_.getMessageOrBuilder();
+        } else {
+          return close_;
+        }
+      }
+      /**
+       * <code>optional .paymentchannels.Close close = 9;</code>
+       */
+      private com.google.protobuf.SingleFieldBuilder<
+          org.bitcoin.paymentchannel.Protos.Close, org.bitcoin.paymentchannel.Protos.Close.Builder, org.bitcoin.paymentchannel.Protos.CloseOrBuilder> 
+          getCloseFieldBuilder() {
+        if (closeBuilder_ == null) {
+          closeBuilder_ = new com.google.protobuf.SingleFieldBuilder<
+              org.bitcoin.paymentchannel.Protos.Close, org.bitcoin.paymentchannel.Protos.Close.Builder, org.bitcoin.paymentchannel.Protos.CloseOrBuilder>(
+                  close_,
+                  getParentForChildren(),
+                  isClean());
+          close_ = null;
+        }
+        return closeBuilder_;
+      }
+
       // optional .paymentchannels.Error error = 10;
       private org.bitcoin.paymentchannel.Protos.Error error_ = org.bitcoin.paymentchannel.Protos.Error.getDefaultInstance();
       private com.google.protobuf.SingleFieldBuilder<
@@ -2241,7 +2457,7 @@ public final class Protos {
        * <code>optional .paymentchannels.Error error = 10;</code>
        */
       public boolean hasError() {
-        return ((bitField0_ & 0x00000100) == 0x00000100);
+        return ((bitField0_ & 0x00000200) == 0x00000200);
       }
       /**
        * <code>optional .paymentchannels.Error error = 10;</code>
@@ -2266,7 +2482,7 @@ public final class Protos {
         } else {
           errorBuilder_.setMessage(value);
         }
-        bitField0_ |= 0x00000100;
+        bitField0_ |= 0x00000200;
         return this;
       }
       /**
@@ -2280,7 +2496,7 @@ public final class Protos {
         } else {
           errorBuilder_.setMessage(builderForValue.build());
         }
-        bitField0_ |= 0x00000100;
+        bitField0_ |= 0x00000200;
         return this;
       }
       /**
@@ -2288,7 +2504,7 @@ public final class Protos {
        */
       public Builder mergeError(org.bitcoin.paymentchannel.Protos.Error value) {
         if (errorBuilder_ == null) {
-          if (((bitField0_ & 0x00000100) == 0x00000100) &&
+          if (((bitField0_ & 0x00000200) == 0x00000200) &&
               error_ != org.bitcoin.paymentchannel.Protos.Error.getDefaultInstance()) {
             error_ =
               org.bitcoin.paymentchannel.Protos.Error.newBuilder(error_).mergeFrom(value).buildPartial();
@@ -2299,7 +2515,7 @@ public final class Protos {
         } else {
           errorBuilder_.mergeFrom(value);
         }
-        bitField0_ |= 0x00000100;
+        bitField0_ |= 0x00000200;
         return this;
       }
       /**
@@ -2312,14 +2528,14 @@ public final class Protos {
         } else {
           errorBuilder_.clear();
         }
-        bitField0_ = (bitField0_ & ~0x00000100);
+        bitField0_ = (bitField0_ & ~0x00000200);
         return this;
       }
       /**
        * <code>optional .paymentchannels.Error error = 10;</code>
        */
       public org.bitcoin.paymentchannel.Protos.Error.Builder getErrorBuilder() {
-        bitField0_ |= 0x00000100;
+        bitField0_ |= 0x00000200;
         onChanged();
         return getErrorFieldBuilder().getBuilder();
       }
@@ -6447,6 +6663,453 @@ public final class Protos {
     // @@protoc_insertion_point(class_scope:paymentchannels.UpdatePayment)
   }
 
+  public interface CloseOrBuilder
+      extends com.google.protobuf.MessageOrBuilder {
+
+    // required bytes tx = 3;
+    /**
+     * <code>required bytes tx = 3;</code>
+     *
+     * <pre>
+     * A copy of the fully signed final contract that closes the channel. The client can verify
+     * the transaction is correct and then commit it to their wallet.
+     * </pre>
+     */
+    boolean hasTx();
+    /**
+     * <code>required bytes tx = 3;</code>
+     *
+     * <pre>
+     * A copy of the fully signed final contract that closes the channel. The client can verify
+     * the transaction is correct and then commit it to their wallet.
+     * </pre>
+     */
+    com.google.protobuf.ByteString getTx();
+  }
+  /**
+   * Protobuf type {@code paymentchannels.Close}
+   */
+  public static final class Close extends
+      com.google.protobuf.GeneratedMessage
+      implements CloseOrBuilder {
+    // Use Close.newBuilder() to construct.
+    private Close(com.google.protobuf.GeneratedMessage.Builder<?> builder) {
+      super(builder);
+      this.unknownFields = builder.getUnknownFields();
+    }
+    private Close(boolean noInit) { this.unknownFields = com.google.protobuf.UnknownFieldSet.getDefaultInstance(); }
+
+    private static final Close defaultInstance;
+    public static Close getDefaultInstance() {
+      return defaultInstance;
+    }
+
+    public Close getDefaultInstanceForType() {
+      return defaultInstance;
+    }
+
+    private final com.google.protobuf.UnknownFieldSet unknownFields;
+    @java.lang.Override
+    public final com.google.protobuf.UnknownFieldSet
+        getUnknownFields() {
+      return this.unknownFields;
+    }
+    private Close(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      initFields();
+      int mutable_bitField0_ = 0;
+      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+          com.google.protobuf.UnknownFieldSet.newBuilder();
+      try {
+        boolean done = false;
+        while (!done) {
+          int tag = input.readTag();
+          switch (tag) {
+            case 0:
+              done = true;
+              break;
+            default: {
+              if (!parseUnknownField(input, unknownFields,
+                                     extensionRegistry, tag)) {
+                done = true;
+              }
+              break;
+            }
+            case 26: {
+              bitField0_ |= 0x00000001;
+              tx_ = input.readBytes();
+              break;
+            }
+          }
+        }
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        throw e.setUnfinishedMessage(this);
+      } catch (java.io.IOException e) {
+        throw new com.google.protobuf.InvalidProtocolBufferException(
+            e.getMessage()).setUnfinishedMessage(this);
+      } finally {
+        this.unknownFields = unknownFields.build();
+        makeExtensionsImmutable();
+      }
+    }
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return org.bitcoin.paymentchannel.Protos.internal_static_paymentchannels_Close_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessage.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return org.bitcoin.paymentchannel.Protos.internal_static_paymentchannels_Close_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              org.bitcoin.paymentchannel.Protos.Close.class, org.bitcoin.paymentchannel.Protos.Close.Builder.class);
+    }
+
+    public static com.google.protobuf.Parser<Close> PARSER =
+        new com.google.protobuf.AbstractParser<Close>() {
+      public Close parsePartialFrom(
+          com.google.protobuf.CodedInputStream input,
+          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+          throws com.google.protobuf.InvalidProtocolBufferException {
+        return new Close(input, extensionRegistry);
+      }
+    };
+
+    @java.lang.Override
+    public com.google.protobuf.Parser<Close> getParserForType() {
+      return PARSER;
+    }
+
+    private int bitField0_;
+    // required bytes tx = 3;
+    public static final int TX_FIELD_NUMBER = 3;
+    private com.google.protobuf.ByteString tx_;
+    /**
+     * <code>required bytes tx = 3;</code>
+     *
+     * <pre>
+     * A copy of the fully signed final contract that closes the channel. The client can verify
+     * the transaction is correct and then commit it to their wallet.
+     * </pre>
+     */
+    public boolean hasTx() {
+      return ((bitField0_ & 0x00000001) == 0x00000001);
+    }
+    /**
+     * <code>required bytes tx = 3;</code>
+     *
+     * <pre>
+     * A copy of the fully signed final contract that closes the channel. The client can verify
+     * the transaction is correct and then commit it to their wallet.
+     * </pre>
+     */
+    public com.google.protobuf.ByteString getTx() {
+      return tx_;
+    }
+
+    private void initFields() {
+      tx_ = com.google.protobuf.ByteString.EMPTY;
+    }
+    private byte memoizedIsInitialized = -1;
+    public final boolean isInitialized() {
+      byte isInitialized = memoizedIsInitialized;
+      if (isInitialized != -1) return isInitialized == 1;
+
+      if (!hasTx()) {
+        memoizedIsInitialized = 0;
+        return false;
+      }
+      memoizedIsInitialized = 1;
+      return true;
+    }
+
+    public void writeTo(com.google.protobuf.CodedOutputStream output)
+                        throws java.io.IOException {
+      getSerializedSize();
+      if (((bitField0_ & 0x00000001) == 0x00000001)) {
+        output.writeBytes(3, tx_);
+      }
+      getUnknownFields().writeTo(output);
+    }
+
+    private int memoizedSerializedSize = -1;
+    public int getSerializedSize() {
+      int size = memoizedSerializedSize;
+      if (size != -1) return size;
+
+      size = 0;
+      if (((bitField0_ & 0x00000001) == 0x00000001)) {
+        size += com.google.protobuf.CodedOutputStream
+          .computeBytesSize(3, tx_);
+      }
+      size += getUnknownFields().getSerializedSize();
+      memoizedSerializedSize = size;
+      return size;
+    }
+
+    private static final long serialVersionUID = 0L;
+    @java.lang.Override
+    protected java.lang.Object writeReplace()
+        throws java.io.ObjectStreamException {
+      return super.writeReplace();
+    }
+
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        com.google.protobuf.ByteString data)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        com.google.protobuf.ByteString data,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data, extensionRegistry);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(byte[] data)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        byte[] data,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data, extensionRegistry);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(java.io.InputStream input)
+        throws java.io.IOException {
+      return PARSER.parseFrom(input);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        java.io.InputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return PARSER.parseFrom(input, extensionRegistry);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseDelimitedFrom(java.io.InputStream input)
+        throws java.io.IOException {
+      return PARSER.parseDelimitedFrom(input);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseDelimitedFrom(
+        java.io.InputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return PARSER.parseDelimitedFrom(input, extensionRegistry);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        com.google.protobuf.CodedInputStream input)
+        throws java.io.IOException {
+      return PARSER.parseFrom(input);
+    }
+    public static org.bitcoin.paymentchannel.Protos.Close parseFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return PARSER.parseFrom(input, extensionRegistry);
+    }
+
+    public static Builder newBuilder() { return Builder.create(); }
+    public Builder newBuilderForType() { return newBuilder(); }
+    public static Builder newBuilder(org.bitcoin.paymentchannel.Protos.Close prototype) {
+      return newBuilder().mergeFrom(prototype);
+    }
+    public Builder toBuilder() { return newBuilder(this); }
+
+    @java.lang.Override
+    protected Builder newBuilderForType(
+        com.google.protobuf.GeneratedMessage.BuilderParent parent) {
+      Builder builder = new Builder(parent);
+      return builder;
+    }
+    /**
+     * Protobuf type {@code paymentchannels.Close}
+     */
+    public static final class Builder extends
+        com.google.protobuf.GeneratedMessage.Builder<Builder>
+       implements org.bitcoin.paymentchannel.Protos.CloseOrBuilder {
+      public static final com.google.protobuf.Descriptors.Descriptor
+          getDescriptor() {
+        return org.bitcoin.paymentchannel.Protos.internal_static_paymentchannels_Close_descriptor;
+      }
+
+      protected com.google.protobuf.GeneratedMessage.FieldAccessorTable
+          internalGetFieldAccessorTable() {
+        return org.bitcoin.paymentchannel.Protos.internal_static_paymentchannels_Close_fieldAccessorTable
+            .ensureFieldAccessorsInitialized(
+                org.bitcoin.paymentchannel.Protos.Close.class, org.bitcoin.paymentchannel.Protos.Close.Builder.class);
+      }
+
+      // Construct using org.bitcoin.paymentchannel.Protos.Close.newBuilder()
+      private Builder() {
+        maybeForceBuilderInitialization();
+      }
+
+      private Builder(
+          com.google.protobuf.GeneratedMessage.BuilderParent parent) {
+        super(parent);
+        maybeForceBuilderInitialization();
+      }
+      private void maybeForceBuilderInitialization() {
+        if (com.google.protobuf.GeneratedMessage.alwaysUseFieldBuilders) {
+        }
+      }
+      private static Builder create() {
+        return new Builder();
+      }
+
+      public Builder clear() {
+        super.clear();
+        tx_ = com.google.protobuf.ByteString.EMPTY;
+        bitField0_ = (bitField0_ & ~0x00000001);
+        return this;
+      }
+
+      public Builder clone() {
+        return create().mergeFrom(buildPartial());
+      }
+
+      public com.google.protobuf.Descriptors.Descriptor
+          getDescriptorForType() {
+        return org.bitcoin.paymentchannel.Protos.internal_static_paymentchannels_Close_descriptor;
+      }
+
+      public org.bitcoin.paymentchannel.Protos.Close getDefaultInstanceForType() {
+        return org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance();
+      }
+
+      public org.bitcoin.paymentchannel.Protos.Close build() {
+        org.bitcoin.paymentchannel.Protos.Close result = buildPartial();
+        if (!result.isInitialized()) {
+          throw newUninitializedMessageException(result);
+        }
+        return result;
+      }
+
+      public org.bitcoin.paymentchannel.Protos.Close buildPartial() {
+        org.bitcoin.paymentchannel.Protos.Close result = new org.bitcoin.paymentchannel.Protos.Close(this);
+        int from_bitField0_ = bitField0_;
+        int to_bitField0_ = 0;
+        if (((from_bitField0_ & 0x00000001) == 0x00000001)) {
+          to_bitField0_ |= 0x00000001;
+        }
+        result.tx_ = tx_;
+        result.bitField0_ = to_bitField0_;
+        onBuilt();
+        return result;
+      }
+
+      public Builder mergeFrom(com.google.protobuf.Message other) {
+        if (other instanceof org.bitcoin.paymentchannel.Protos.Close) {
+          return mergeFrom((org.bitcoin.paymentchannel.Protos.Close)other);
+        } else {
+          super.mergeFrom(other);
+          return this;
+        }
+      }
+
+      public Builder mergeFrom(org.bitcoin.paymentchannel.Protos.Close other) {
+        if (other == org.bitcoin.paymentchannel.Protos.Close.getDefaultInstance()) return this;
+        if (other.hasTx()) {
+          setTx(other.getTx());
+        }
+        this.mergeUnknownFields(other.getUnknownFields());
+        return this;
+      }
+
+      public final boolean isInitialized() {
+        if (!hasTx()) {
+          
+          return false;
+        }
+        return true;
+      }
+
+      public Builder mergeFrom(
+          com.google.protobuf.CodedInputStream input,
+          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+          throws java.io.IOException {
+        org.bitcoin.paymentchannel.Protos.Close parsedMessage = null;
+        try {
+          parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+          parsedMessage = (org.bitcoin.paymentchannel.Protos.Close) e.getUnfinishedMessage();
+          throw e;
+        } finally {
+          if (parsedMessage != null) {
+            mergeFrom(parsedMessage);
+          }
+        }
+        return this;
+      }
+      private int bitField0_;
+
+      // required bytes tx = 3;
+      private com.google.protobuf.ByteString tx_ = com.google.protobuf.ByteString.EMPTY;
+      /**
+       * <code>required bytes tx = 3;</code>
+       *
+       * <pre>
+       * A copy of the fully signed final contract that closes the channel. The client can verify
+       * the transaction is correct and then commit it to their wallet.
+       * </pre>
+       */
+      public boolean hasTx() {
+        return ((bitField0_ & 0x00000001) == 0x00000001);
+      }
+      /**
+       * <code>required bytes tx = 3;</code>
+       *
+       * <pre>
+       * A copy of the fully signed final contract that closes the channel. The client can verify
+       * the transaction is correct and then commit it to their wallet.
+       * </pre>
+       */
+      public com.google.protobuf.ByteString getTx() {
+        return tx_;
+      }
+      /**
+       * <code>required bytes tx = 3;</code>
+       *
+       * <pre>
+       * A copy of the fully signed final contract that closes the channel. The client can verify
+       * the transaction is correct and then commit it to their wallet.
+       * </pre>
+       */
+      public Builder setTx(com.google.protobuf.ByteString value) {
+        if (value == null) {
+    throw new NullPointerException();
+  }
+  bitField0_ |= 0x00000001;
+        tx_ = value;
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>required bytes tx = 3;</code>
+       *
+       * <pre>
+       * A copy of the fully signed final contract that closes the channel. The client can verify
+       * the transaction is correct and then commit it to their wallet.
+       * </pre>
+       */
+      public Builder clearTx() {
+        bitField0_ = (bitField0_ & ~0x00000001);
+        tx_ = getDefaultInstance().getTx();
+        onChanged();
+        return this;
+      }
+
+      // @@protoc_insertion_point(builder_scope:paymentchannels.Close)
+    }
+
+    static {
+      defaultInstance = new Close(true);
+      defaultInstance.initFields();
+    }
+
+    // @@protoc_insertion_point(class_scope:paymentchannels.Close)
+  }
+
   public interface ErrorOrBuilder
       extends com.google.protobuf.MessageOrBuilder {
 
@@ -7285,6 +7948,11 @@ public final class Protos {
   private static
     com.google.protobuf.GeneratedMessage.FieldAccessorTable
       internal_static_paymentchannels_UpdatePayment_fieldAccessorTable;
+  private static com.google.protobuf.Descriptors.Descriptor
+    internal_static_paymentchannels_Close_descriptor;
+  private static
+    com.google.protobuf.GeneratedMessage.FieldAccessorTable
+      internal_static_paymentchannels_Close_fieldAccessorTable;
   private static com.google.protobuf.Descriptors.Descriptor
     internal_static_paymentchannels_Error_descriptor;
   private static
@@ -7300,7 +7968,7 @@ public final class Protos {
   static {
     java.lang.String[] descriptorData = {
       "\n\024paymentchannel.proto\022\017paymentchannels\"" +
-      "\274\005\n\024TwoWayChannelMessage\022?\n\004type\030\001 \002(\01621" +
+      "\343\005\n\024TwoWayChannelMessage\022?\n\004type\030\001 \002(\01621" +
       ".paymentchannels.TwoWayChannelMessage.Me" +
       "ssageType\0226\n\016client_version\030\002 \001(\0132\036.paym" +
       "entchannels.ClientVersion\0226\n\016server_vers" +
@@ -7311,31 +7979,32 @@ public final class Protos {
       "\006 \001(\0132\035.paymentchannels.ReturnRefund\022:\n\020",
       "provide_contract\030\007 \001(\0132 .paymentchannels" +
       ".ProvideContract\0226\n\016update_payment\030\010 \001(\013" +
-      "2\036.paymentchannels.UpdatePayment\022%\n\005erro" +
+      "2\036.paymentchannels.UpdatePayment\022%\n\005clos" +
-      "r\030\n \001(\0132\026.paymentchannels.Error\"\274\001\n\013Mess" +
+      "e\030\t \001(\0132\026.paymentchannels.Close\022%\n\005error" +
-      "ageType\022\022\n\016CLIENT_VERSION\020\001\022\022\n\016SERVER_VE" +
+      "\030\n \001(\0132\026.paymentchannels.Error\"\274\001\n\013Messa" +
-      "RSION\020\002\022\014\n\010INITIATE\020\003\022\022\n\016PROVIDE_REFUND\020" +
+      "geType\022\022\n\016CLIENT_VERSION\020\001\022\022\n\016SERVER_VER" +
-      "\004\022\021\n\rRETURN_REFUND\020\005\022\024\n\020PROVIDE_CONTRACT" +
+      "SION\020\002\022\014\n\010INITIATE\020\003\022\022\n\016PROVIDE_REFUND\020\004" +
-      "\020\006\022\020\n\014CHANNEL_OPEN\020\007\022\022\n\016UPDATE_PAYMENT\020\010" +
+      "\022\021\n\rRETURN_REFUND\020\005\022\024\n\020PROVIDE_CONTRACT\020" +
-      "\022\t\n\005CLOSE\020\t\022\t\n\005ERROR\020\n\"X\n\rClientVersion\022" +
+      "\006\022\020\n\014CHANNEL_OPEN\020\007\022\022\n\016UPDATE_PAYMENT\020\010\022" +
-      "\r\n\005major\030\001 \002(\005\022\020\n\005minor\030\002 \001(\005:\0010\022&\n\036prev",
+      "\t\n\005CLOSE\020\t\022\t\n\005ERROR\020\n\"X\n\rClientVersion\022\r",
-      "ious_channel_contract_hash\030\003 \001(\014\"0\n\rServ" +
+      "\n\005major\030\001 \002(\005\022\020\n\005minor\030\002 \001(\005:\0010\022&\n\036previ" +
-      "erVersion\022\r\n\005major\030\001 \002(\005\022\020\n\005minor\030\002 \001(\005:" +
+      "ous_channel_contract_hash\030\003 \001(\014\"0\n\rServe" +
-      "\0010\"]\n\010Initiate\022\024\n\014multisig_key\030\001 \002(\014\022!\n\031" +
+      "rVersion\022\r\n\005major\030\001 \002(\005\022\020\n\005minor\030\002 \001(\005:\001" +
-      "min_accepted_channel_size\030\002 \002(\004\022\030\n\020expir" +
+      "0\"]\n\010Initiate\022\024\n\014multisig_key\030\001 \002(\014\022!\n\031m" +
-      "e_time_secs\030\003 \002(\004\"1\n\rProvideRefund\022\024\n\014mu" +
+      "in_accepted_channel_size\030\002 \002(\004\022\030\n\020expire" +
-      "ltisig_key\030\001 \002(\014\022\n\n\002tx\030\002 \002(\014\"!\n\014ReturnRe" +
+      "_time_secs\030\003 \002(\004\"1\n\rProvideRefund\022\024\n\014mul" +
-      "fund\022\021\n\tsignature\030\001 \002(\014\"\035\n\017ProvideContra" +
+      "tisig_key\030\001 \002(\014\022\n\n\002tx\030\002 \002(\014\"!\n\014ReturnRef" +
-      "ct\022\n\n\002tx\030\001 \002(\014\"?\n\rUpdatePayment\022\033\n\023clien" +
+      "und\022\021\n\tsignature\030\001 \002(\014\"\035\n\017ProvideContrac" +
-      "t_change_value\030\001 \002(\004\022\021\n\tsignature\030\002 \002(\014\"" +
+      "t\022\n\n\002tx\030\001 \002(\014\"?\n\rUpdatePayment\022\033\n\023client" +
-      "\363\001\n\005Error\0225\n\004code\030\001 \001(\0162 .paymentchannel",
+      "_change_value\030\001 \002(\004\022\021\n\tsignature\030\002 \002(\014\"\023",
-      "s.Error.ErrorCode:\005OTHER\022\023\n\013explanation\030" +
+      "\n\005Close\022\n\n\002tx\030\003 \002(\014\"\363\001\n\005Error\0225\n\004code\030\001 " +
-      "\002 \001(\t\"\235\001\n\tErrorCode\022\013\n\007TIMEOUT\020\001\022\020\n\014SYNT" +
+      "\001(\0162 .paymentchannels.Error.ErrorCode:\005O" +
-      "AX_ERROR\020\002\022\031\n\025NO_ACCEPTABLE_VERSION\020\003\022\023\n" +
+      "THER\022\023\n\013explanation\030\002 \001(\t\"\235\001\n\tErrorCode\022" +
-      "\017BAD_TRANSACTION\020\004\022\031\n\025TIME_WINDOW_TOO_LA" +
+      "\013\n\007TIMEOUT\020\001\022\020\n\014SYNTAX_ERROR\020\002\022\031\n\025NO_ACC" +
-      "RGE\020\005\022\033\n\027CHANNEL_VALUE_TOO_LARGE\020\006\022\t\n\005OT" +
+      "EPTABLE_VERSION\020\003\022\023\n\017BAD_TRANSACTION\020\004\022\031" +
-      "HER\020\007B$\n\032org.bitcoin.paymentchannelB\006Pro" +
+      "\n\025TIME_WINDOW_TOO_LARGE\020\005\022\033\n\027CHANNEL_VAL" +
-      "tos"
+      "UE_TOO_LARGE\020\006\022\t\n\005OTHER\020\007B$\n\032org.bitcoin" +
+      ".paymentchannelB\006Protos"
     };
     com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
       new com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner() {
@@ -7347,7 +8016,7 @@ public final class Protos {
           internal_static_paymentchannels_TwoWayChannelMessage_fieldAccessorTable = new
             com.google.protobuf.GeneratedMessage.FieldAccessorTable(
               internal_static_paymentchannels_TwoWayChannelMessage_descriptor,
-              new java.lang.String[] { "Type", "ClientVersion", "ServerVersion", "Initiate", "ProvideRefund", "ReturnRefund", "ProvideContract", "UpdatePayment", "Error", });
+              new java.lang.String[] { "Type", "ClientVersion", "ServerVersion", "Initiate", "ProvideRefund", "ReturnRefund", "ProvideContract", "UpdatePayment", "Close", "Error", });
           internal_static_paymentchannels_ClientVersion_descriptor =
             getDescriptor().getMessageTypes().get(1);
           internal_static_paymentchannels_ClientVersion_fieldAccessorTable = new
@@ -7390,8 +8059,14 @@ public final class Protos {
             com.google.protobuf.GeneratedMessage.FieldAccessorTable(
               internal_static_paymentchannels_UpdatePayment_descriptor,
               new java.lang.String[] { "ClientChangeValue", "Signature", });
-          internal_static_paymentchannels_Error_descriptor =
+          internal_static_paymentchannels_Close_descriptor =
             getDescriptor().getMessageTypes().get(8);
+          internal_static_paymentchannels_Close_fieldAccessorTable = new
+            com.google.protobuf.GeneratedMessage.FieldAccessorTable(
+              internal_static_paymentchannels_Close_descriptor,
+              new java.lang.String[] { "Tx", });
+          internal_static_paymentchannels_Error_descriptor =
+            getDescriptor().getMessageTypes().get(9);
           internal_static_paymentchannels_Error_fieldAccessorTable = new
             com.google.protobuf.GeneratedMessage.FieldAccessorTable(
               internal_static_paymentchannels_Error_descriptor,

core/src/paymentchannel.proto

@@ -47,15 +47,21 @@ message TwoWayChannelMessage {
         // message.
         CHANNEL_OPEN = 7;
         UPDATE_PAYMENT = 8;
-        // Note that there are no optional fields set for CLOSE, it is sent by either party to
+        // Either side can send this message. If the client sends it to the server, then the server
-        // indicate that the channel is now closed and no further updates can happen. After this,
+        // takes the most recent signature it received in an UPDATE_PAYMENT and uses it to create a
-        // the secondary takes the most recent signature it received in an UPDATE_PAYMENT and
+        // valid transaction, which it then broadcasts on the network.
-        // uses it to create a valid transaction, which it then broadcasts on the network.
+        //
+        // If the server sends it to the client, then it can either be a simple "good bye" message or
+        // it can include the fully signed close transaction and give it back so the client can
+        // eventually broadcast it as well, in case the server fails to do so for some reason (and
+        // more usefully so the client can build on it). In that case the server replies to a CLOSE
+        // with another CLOSE and then disconnects.
         CLOSE = 9;
 
         // Used to indicate an error condition.
         // Both parties should make an effort to send either an ERROR or a CLOSE immediately
-        // before closing the socket (unless they just received an ERROR or a CLOSE)
+        // before closing the socket (unless they just received an ERROR or a CLOSE). This is important
+        // because the protocol may not run over TCP.
         ERROR = 10;
     };
 
@@ -72,6 +78,7 @@ message TwoWayChannelMessage {
     optional ReturnRefund return_refund = 6;
     optional ProvideContract provide_contract = 7;
     optional UpdatePayment update_payment = 8;
+    optional Close close = 9;
 
     optional Error error = 10;
 }
@@ -185,6 +192,11 @@ message UpdatePayment {
     required bytes signature = 2;
 }
 
+message Close {
+    // A copy of the fully signed final contract that closes the channel. The client can verify
+    // the transaction is correct and then commit it to their wallet.
+    required bytes tx = 3;
+}
 
 // An Error can be sent by either party at any time
 // Both parties should make an effort to send either an ERROR or a CLOSE immediately before

core/src/test/java/com/google/bitcoin/protocols/channels/ChannelConnectionTest.java

@@ -644,13 +644,23 @@ public class ChannelConnectionTest extends TestWithWallet {
             client.incrementPayment(Utils.CENT);
             client.incrementPayment(Utils.CENT);
             server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
+            pair.serverRecorder.q.take();
             server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
+            pair.serverRecorder.q.take();
             server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
+            pair.serverRecorder.q.take();
+
             // Close it and verify it's considered to be closed.
             broadcastTxPause.release();
             client.close();
             server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.CLOSE));
             Transaction close = broadcasts.take();
+            // Server sends back the close TX it just broadcast.
+            final Protos.TwoWayChannelMessage closeMsg = pair.serverRecorder.checkNextMsg(MessageType.CLOSE);
+            final Transaction closeTx = new Transaction(params, closeMsg.getClose().getTx().toByteArray());
+            assertEquals(close, closeTx);
+            client.receiveMessage(closeMsg);
+            assertNotNull(wallet.getTransaction(closeTx.getHash()));   // Close TX entered the wallet.
             sendMoneyToWallet(close, AbstractBlockChain.NewBlockType.BEST_CHAIN);
             client.connectionClosed();
             server.connectionClosed();

core/src/test/java/com/google/bitcoin/protocols/channels/PaymentChannelStateTest.java

@@ -20,7 +20,6 @@ import com.google.bitcoin.core.*;
 import com.google.bitcoin.script.Script;
 import com.google.bitcoin.script.ScriptBuilder;
 import com.google.bitcoin.utils.TestWithWallet;
-import com.google.bitcoin.wallet.DefaultCoinSelector;
 import com.google.common.collect.Lists;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
@@ -189,29 +188,19 @@ public class PaymentChannelStateTest extends TestWithWallet {
         final TxFuturePair pair2 = broadcasts.take();
         Transaction closeTx = pair2.tx;
         pair2.future.set(closeTx);
+        final Transaction reserializedCloseTx = new Transaction(params, closeTx.bitcoinSerialize());
         assertEquals(PaymentChannelServerState.State.CLOSED, serverState.getState());
+        // ... and on the client side.
+        wallet.receivePending(reserializedCloseTx, null);
+        assertEquals(PaymentChannelClientState.State.CLOSED, clientState.getState());
 
         // Create a block with the payment transaction in it and give it to both wallets
-        chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), new Transaction(params, closeTx.bitcoinSerialize())));
+        chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), reserializedCloseTx));
 
-        assertEquals(size.multiply(BigInteger.valueOf(5)), serverWallet.getBalance(new DefaultCoinSelector() {
+        assertEquals(size.multiply(BigInteger.valueOf(5)), serverWallet.getBalance());
-            @Override
-            protected boolean shouldSelect(Transaction tx) {
-                if (tx.getConfidence().getConfidenceType() == TransactionConfidence.ConfidenceType.BUILDING)
-                    return true;
-                return false;
-            }
-        }));
         assertEquals(0, serverWallet.getPendingTransactions().size());
 
-        assertEquals(Utils.COIN.subtract(size.multiply(BigInteger.valueOf(5))), wallet.getBalance(new DefaultCoinSelector() {
+        assertEquals(Utils.COIN.subtract(size.multiply(BigInteger.valueOf(5))), wallet.getBalance());
-            @Override
-            protected boolean shouldSelect(Transaction tx) {
-                if (tx.getConfidence().getConfidenceType() == TransactionConfidence.ConfidenceType.BUILDING)
-                    return true;
-                return false;
-            }
-        }));
         assertEquals(0, wallet.getPendingTransactions().size());
         assertEquals(3, wallet.getTransactions(false).size());