不使用netcat服务器从套接字读取Flink中的字符串datastream

Question

我有一个案例场景，其中我有一个流生成器客户机，它正在生成多个流，合并它们并将其发送到socket，我希望Flink程序作为服务器监听它。正如我们所知，服务器必须首先打开，以便它能够监听客户机请求。我尝试使用下面给出的代码来做同样的事情

 public static void main(String[] args)  throws Exception {

    //setting the envrionment variable as StreamExecutionEnvironment
      StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();

        environment.setParallelism(1);


        DataStream<String> stream1 = environment.socketTextStream("localhost", 9000);
        stream1.print();



                //start the execution
     environment.execute(" Started the execution ");



}// main

下面给出了充当客户端的流生成器的代码

    DataStream<Event> stream1  = envrionment
                .addSource(new EventGenerator(2,60,1,1,100, 200 ))
                .name("stream 1")
                .setParallelism(parallelism_for_stream_rr);

    DataStream<Event> stream2  = envrionment
            .addSource(new EventGenerator(3,60,1,2,10, 20 ))
            .name("stream 2")
            .setParallelism(parallelism_for_stream_rr);


    DataStream<Event> stream3  = envrionment
            .addSource(new EventGenerator(5,60,1,3,30, 40 ))
            .name("stream 3")
            .setParallelism(parallelism_for_stream_rr);


    DataStream<Event> merged = stream1.union(stream2,stream3);

    merged.print();



            // sending data to Mobile Cep via socket

            merged.map(new MapFunction<Event, String>() {

                @Override
                public String map(Event event) throws Exception {
                    String tuple = event.toString();


                    return tuple + "\n";

                }
            }).writeToSocket("localhost", 9000, new SimpleStringSchema() );

Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)

Answer 1

Flink的套接字源和它的接收器都不会启动TCP服务器并等待传入连接。它们都是连接到已经启动的TCP服务器的客户端。这也是为什么在启动作业之前必须启动netcat的原因。如果您想从套接字写入和读取，那么您必须编写一个TCP服务器，该服务器可以缓冲传入的数据，并在客户机连接到该数据时转发这些数据。