Java客户端/服务器套接字问题

Question

I'm learning Java socket programming, and I'm pretty positive my code is correct, but for some reason the server and the client don't communicate. I'm not quite sure if they're even connecting. Here is what I've done so far.

Server:

public static void main(String[] args) throws Exception
{
    Main_Server server = new Main_Server();
    server.run();
}

public void run() throws Exception
{
    ServerSocket server = new ServerSocket(444); //Port
    Socket sSocket = server.accept();

    BufferedReader bfr = new BufferedReader(new InputStreamReader(sSocket.getInputStream()));

    String clientMessage = bfr.readLine();
    System.out.println("Client: "+clientMessage);

    if (clientMessage != null)
    {
        PrintStream ps = new PrintStream(sSocket.getOutputStream());
        ps.println("Message Received.");
    }
}

Client:

public static void main(String[] args) throws Exception
{
    Client_One client = new Client_One();
    client.run();
}

public void run() throws Exception
{
    Socket clientSocket = new Socket("localhost", 444);

    PrintStream ps = new PrintStream(clientSocket.getOutputStream());
    ps.println("Hello, server.");

    BufferedReader bfr = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
    String serverMessage = bfr.readLine();
    System.out.println("Server: "+serverMessage);
}

So I run the server first and the client after (I'm currently using NetBeans IDE 8.1). The programs run and just sit there, but nothing happens after that. Why is this? I just have two empty consoles. Thank you for your time.

Answer 1

If you use a Buffer you need to flush it or close it, otherwise if the buffer is not full the data remains in the buffer. It is ok also to close it because as you can see from the javadoc closing a stream will also flush it.

From the javadoc of OutputStream you can see what flushing means:

Flushes this output stream and forces any buffered output bytes to be written out .

Note: additionally remember to close both input and output streams when you finished to use them, otherwise you still have not properly closed resources using memory.