Java 在后台接收消息

Java客户端服务器。 有必要在后台接收来自客户端的消息。 我正在尝试在后台接收消息：

public Server() throws IOException {
           try {
        serverSocket=new ServerSocket(1234);
        fromclient= serverSocket.accept();
        System.out.println("Socket created");
    } catch (IOException e) {
        e.printStackTrace();
        System.out.println("Socket not created");
    }
    try {
        in  = new BufferedReader(new
                InputStreamReader(fromclient.getInputStream()));
    } catch (IOException e) {
        e.printStackTrace();
    }
    out = new PrintWriter(fromclient.getOutputStream(),true);
    String         input,output;
}

接地部分：

 public void run(ServerSocket welcomeSocket) throws IOException {
        Socket connectionSocket = welcomeSocket.
                accept();
        BufferedReader inFromClient =
                new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
        DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
        clientSentence = inFromClient.readLine();
        System.out.println(clientSentence);
        capitalizedSentence =
                clientSentence.toUpperCase() + '\n';
        outToClient.writeBytes(capitalizedSentence);
    }

并在客户端发送消息：

  Client client=new Client();
    client.Connect();
   client.sendToServer("text test");
   Run run=new Run();

  void run() throws IOException {
            BufferedReader inFromUser =
                    new BufferedReader(
                            new InputStreamReader(System.in));
            Socket clientSocket = new Socket ("127.0.0.1",6789);
            DataOutputStream outToServer =
                    new DataOutputStream(
                            clientSocket.getOutputStream());
            BufferedReader inFromServer =
                    new BufferedReader(
                            new InputStreamReader(
                                    clientSocket.getInputStream()));
            sentence = inFromUser.readLine();
           // while (true) {
                outToServer.writeBytes(sentence + "\n");
                modifiedSentence = inFromServer.readLine();
                System.out.println("FROM SERVER: " + modifiedSentence);
            //}
            //     clientSocket.close();
        }

---

但是什么也没发生。

您在端口1234上打开了一个服务器套接字，然后将该套接字连接到6789。尝试使用相同的端口：）