Add Echo Server/Client Example

Summary:
I got a lot of feedback from my blog post saying there wasn't much examples to learn Wangle so I thought I'd write a few examples. I will start off with the most basic example - an Echo Server/Client.
Closes #21

Reviewed By: djwatson

Differential Revision: D2816631

Pulled By: viswanathgs

fb-gh-sync-id: 24027b37bda5bd7962e3ae2e2fcdcbe9a2ff0961

wangle/CMakeLists.txt

@@ -159,6 +159,10 @@ endif()
 option(BUILD_EXAMPLES "BUILD_EXAMPLES" OFF)
 
 if(BUILD_EXAMPLES)
+  add_executable(EchoClient example/echo/EchoClient.cpp)
+  target_link_libraries(EchoClient wangle)
+  add_executable(EchoServer example/echo/EchoServer.cpp)
+  target_link_libraries(EchoServer wangle)
   add_executable(TelnetClient example/telnet/TelnetClient.cpp)
   target_link_libraries(TelnetClient wangle)
   add_executable(TelnetServer example/telnet/TelnetServer.cpp)

wangle/example/echo/EchoClient.cpp

@@ -0,0 +1,86 @@
+/*
+ *  Copyright (c) 2016, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+#include <gflags/gflags.h>
+#include <iostream>
+
+#include <wangle/bootstrap/ClientBootstrap.h>
+#include <wangle/channel/AsyncSocketHandler.h>
+#include <wangle/channel/EventBaseHandler.h>
+#include <wangle/codec/LineBasedFrameDecoder.h>
+#include <wangle/codec/StringCodec.h>
+
+using namespace folly;
+using namespace wangle;
+
+DEFINE_int32(port, 8080, "echo server port");
+DEFINE_string(host, "::1", "echo server address");
+
+typedef Pipeline<folly::IOBufQueue&, std::string> EchoPipeline;
+
+// the handler for receiving messages back from the server
+class EchoHandler : public HandlerAdapter<std::string> {
+ public:
+  virtual void read(Context* ctx, std::string msg) override {
+    std::cout << "received back: " << msg;
+  }
+  virtual void readException(Context* ctx, exception_wrapper e) override {
+    std::cout << exceptionStr(e) << std::endl;
+    close(ctx);
+  }
+  virtual void readEOF(Context* ctx) override {
+    std::cout << "EOF received :(" << std::endl;
+    close(ctx);
+  }
+};
+
+// chains the handlers together to define the response pipeline
+class EchoPipelineFactory : public PipelineFactory<EchoPipeline> {
+ public:
+  EchoPipeline::Ptr newPipeline(std::shared_ptr<AsyncTransportWrapper> sock) {
+    auto pipeline = EchoPipeline::create();
+    pipeline->addBack(AsyncSocketHandler(sock));
+    pipeline->addBack(
+        EventBaseHandler()); // ensure we can write from any thread
+    pipeline->addBack(LineBasedFrameDecoder(8192, false));
+    pipeline->addBack(StringCodec());
+    pipeline->addBack(EchoHandler());
+    pipeline->finalize();
+    return pipeline;
+  }
+};
+
+int main(int argc, char** argv) {
+  google::ParseCommandLineFlags(&argc, &argv, true);
+
+  ClientBootstrap<EchoPipeline> client;
+  client.group(std::make_shared<wangle::IOThreadPoolExecutor>(1));
+  client.pipelineFactory(std::make_shared<EchoPipelineFactory>());
+  auto pipeline = client.connect(SocketAddress(FLAGS_host, FLAGS_port)).get();
+
+  try {
+    while (true) {
+      std::string line;
+      std::getline(std::cin, line);
+      if (line == "") {
+        break;
+      }
+
+      pipeline->write(line + "\r\n").get();
+      if (line == "bye") {
+        pipeline->close();
+        break;
+      }
+    }
+  } catch (const std::exception& e) {
+    std::cout << exceptionStr(e) << std::endl;
+  }
+
+  return 0;
+}

wangle/example/echo/EchoServer.cpp

@@ -0,0 +1,57 @@
+/*
+ *  Copyright (c) 2016, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+#include <gflags/gflags.h>
+
+#include <wangle/bootstrap/ServerBootstrap.h>
+#include <wangle/channel/AsyncSocketHandler.h>
+#include <wangle/codec/LineBasedFrameDecoder.h>
+#include <wangle/codec/StringCodec.h>
+
+using namespace folly;
+using namespace wangle;
+
+DEFINE_int32(port, 8080, "echo server port");
+
+typedef Pipeline<IOBufQueue&, std::string> EchoPipeline;
+
+// the main logic of our echo server; receives a string and writes it straight
+// back
+class EchoHandler : public HandlerAdapter<std::string> {
+ public:
+  virtual void read(Context* ctx, std::string msg) override {
+    std::cout << "handling " << msg << std::endl;
+    write(ctx, msg + "\r\n");
+  }
+};
+
+// where we define the chain of handlers for each messeage received
+class EchoPipelineFactory : public PipelineFactory<EchoPipeline> {
+ public:
+  EchoPipeline::Ptr newPipeline(std::shared_ptr<AsyncTransportWrapper> sock) {
+    auto pipeline = EchoPipeline::create();
+    pipeline->addBack(AsyncSocketHandler(sock));
+    pipeline->addBack(LineBasedFrameDecoder(8192));
+    pipeline->addBack(StringCodec());
+    pipeline->addBack(EchoHandler());
+    pipeline->finalize();
+    return pipeline;
+  }
+};
+
+int main(int argc, char** argv) {
+  google::ParseCommandLineFlags(&argc, &argv, true);
+
+  ServerBootstrap<EchoPipeline> server;
+  server.childPipeline(std::make_shared<EchoPipelineFactory>());
+  server.bind(FLAGS_port);
+  server.waitForStop();
+
+  return 0;
+}