从一个客户端连接到多个套接字

Question

Hi I am new to java client server programming, and I have this modification of a simple program. What I am trying to do is create 2 sockets within the same client, which I then want to use to access 2 sockets on 2 different servers. The server responds with a very simple String, which is then written into a file and displayed to console. This works fine for whichever sockets code I put first. ie if i put clientsocket1 code on top, it receives correctly, but clientsocket2 doesn't get anything. Vice versa if I flip the order. Im testing it all on my own computer so I'm using default IP address "0.0.0.0" and different port numbers for the servers. What could be the issue here?

public static class CustomerClient extends Thread {
    private Socket clientSocket1;
    private Socket clientSocket2;
    String serverInput1;
    String serverInput2;
    String clientCustomerId;

    public CustomerClient(String customerId, String IPAdress1,
            int portNumber1, String IPAdress2, int portNumber2) {
        try {
            clientCustomerId = customerId;
            clientSocket1 = new Socket(IPAdress1, portNumber1);
            clientSocket2 = new Socket(IPAdress2, portNumber2);
        }

        catch (UnknownHostException ex) {
            System.out.println("connection error " + ex);
        } catch (IOException ex) {
            System.out.println("Some other exception" + ex);
        } catch (Exception ex) {
            System.out.println("Some other final exception" + ex);
        }

    }

    public void run() {

        try {



            DataOutputStream outToServer = new DataOutputStream(
                    clientSocket1.getOutputStream());

            BufferedReader inFromServer = new BufferedReader(
                    new InputStreamReader(clientSocket1.getInputStream()));

            while ((serverInput1 = inFromServer.readLine()) != null) {
                BufferedWriter br = new BufferedWriter(new FileWriter(
                        tempFile, true));
                br.write(serverInput1);
                br.newLine();
                // br.append(modifiedSentence);
                System.out.println("FROM SERVER: " + serverInput1);
                br.close();

            }

            DataOutputStream outToServer2 = new DataOutputStream(
                    clientSocket2.getOutputStream());

            BufferedReader inFromServer2 = new BufferedReader(
                    new InputStreamReader(clientSocket2.getInputStream()));

            while ((serverInput2 = inFromServer2.readLine()) != null) {
                BufferedWriter br = new BufferedWriter(new FileWriter(
                        tempFile, true));
                br.write(serverInput2);
                br.newLine();
                // br.append(modifiedSentence);
                System.out.println("FROM SERVER: " + serverInput2);
                br.close();
            }

        } catch (IOException ex) {

        } catch (Exception e) {
            System.out.println("Error" + e);
        } finally {
            try {
                clientSocket1.close();
                clientSocket2.close();
            } catch (Exception e) {
                System.out.println("Error in closing the connection" + e);
            }
        }
    }
}

Answer 1

Isn't, in your case, the client also a server? Because a normal client only connects to one server and that server can handle multiple clients. So, if you want your client to have multiple "connections" to your server, you have two possibilities:

1. Make your client a server itself by giving it a ServerSocket object or
2. Create a kind of protocol, which serializes data in this connection and distributes it correctly