SocketServer和套接字通信，未收到答案

Question

I have made a java ServerSocket. I send a request to it using a Socket Object. The request is delivered to the ServerSocket but the response does not come back.

Server Code :

                Socket startserver = this.wifiserver.accept();

                in = new InputStreamReader(startserver.getInputStream());
                BufferedReader read = new BufferedReader(in);
                String request = read.readLine();
                //System.out.println(request);

                if(request.equals("SNDKEY")){
                    System.out.println("Command is: SNDKEY");
                    out = new PrintWriter(startserver.getOutputStream());
                    out.print("12345678901234567890");
                    out.close();

                }

Client Code:

        Socket connection = new Socket( ip, port );
        writeServer = new PrintWriter(connection.getOutputStream());
        inputStream = new InputStreamReader(connection.getInputStream());
        bufferStream = new BufferedReader(inputStream);
        writeServer.print("SNDKEY");


        this.Key = bufferStream.readLine();

The problem is that the program gets stuck at the command bufferStream.readLine(). I have checked that the request is reaching the server by outputing the line command is: SNDKEY and it always gets printing out. But the key is never received at the user end.

Answer 1

bufferStream.readLine() blocks until a newline is received. But on the server side you are outputting with PrintWriter.print() , which doesn't send any newlines unless you tell it to. So the client waits forever. Either change the print to println, or add a newline character to the end of the message:

out.print("12345678901234567890\n"); 

When you don't want to use newlines in your protocol, you could alternatively use bufferStream.read instead of bufferStream.readLine to return after reading each byte or after reading a specific number of bytes.