content: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
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  package com.google.protobuf;
  
  /**
   * <p>Abstract interface for an RPC channel.  An {@code RpcChannel} represents a
   * communication line to a {@link Service} which can be used to call that
   * {@link Service}'s methods.  The {@link Service} may be running on another
   * machine.  Normally, you should not call an {@code RpcChannel} directly, but
   * instead construct a stub {@link Service} wrapping it.  Example:
   *
   * <pre>
   *   RpcChannel channel = rpcImpl.newChannel("remotehost.example.com:1234");
   *   RpcController controller = rpcImpl.newController();
   *   MyService service = MyService.newStub(channel);
   *   service.myMethod(controller, request, callback);
   * </pre>
   *
   * <p>Starting with version 2.3.0, RPC implementations should not try to build
   * on this, but should instead provide code generator plugins which generate
   * code specific to the particular RPC implementation.  This way the generated
   * code can be more appropriate for the implementation in use and can avoid
   * unnecessary layers of indirection.
   *
   * @author kenton@google.com Kenton Varda
   */
  public interface RpcChannel {
    /**
     * Call the given method of the remote service.  This method is similar to
     * {@code Service.callMethod()} with one important difference:  the caller
     * decides the types of the {@code Message} objects, not the callee.  The
     * request may be of any type as long as
     * {@code request.getDescriptor() == method.getInputType()}.
     * The response passed to the callback will be of the same type as
     * {@code responsePrototype} (which must have
     * {@code getDescriptor() == method.getOutputType()}).
     */
    void callMethod(Descriptors.MethodDescriptor method,
                    RpcController controller,
                    Message request,
                    Message responsePrototype,
                    RpcCallback<Message> done);
  }
  