套接字编程客户端服务器Java

Question

I'm trying to implement a TCP send and receive program between a client and a server. They exchange info. continuously by using a loop. The client send a message first. Without the loop the program work but with the loop, it doesn't. Below are the programs:

public static void main(String[] args)  {
    // SERVER

    try
    {
        ServerSocket s = new ServerSocket(11);
        Socket s1 = null;
        int i=0;
        while (true)
        {
            s1 = s.accept();
            BufferedReader b = new BufferedReader(new InputStreamReader(s1.getInputStream()));
            PrintWriter p = new PrintWriter(new OutputStreamWriter(s1.getOutputStream()));
            String m;
            while ((m=b.readLine())!=null)
            {
                i++;
                System.out.print(m);
                p.print("reply"+i);
            }
        }

    }catch(IOException e){}

}

public static void main(String[] args) throws IOException {
    // CLIENT

    Socket s = new Socket("192.168.100.3",11);
    int i = 0;

    PrintWriter p = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));

    p.print("msg"+i);
    BufferedReader b = new BufferedReader(new InputStreamReader(s.getInputStream()));

    while (true){
        PrintWriter p1 = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));

        BufferedReader b1 = new BufferedReader(new InputStreamReader(s.getInputStream()));

        String m;
        while((m=b1.readLine())!=null)
        {               
            System.out.print(m);
            p1.print("msg"+i);
        }
        i++;
        p1.flush();
    }
}

Answer 1

When you use readLine() it reads up to the end of line.

However, print(x) doesn't write a newline.

If you write and flush a println(x) there is be a new line at the end of your text to read.

Answer 2

Does it make sense to loop and accept on the same socket? as in:

Socket s1 = null;
while (true) {
  s1 = s.accept();

Also, I don't think it would work on port 11 as you have in your code there. Try port numbers above 1024, those are not privileged.

Answer 3

This code will just deadlock. Both ends are reading. Somebody needs to send something first, ensuring that it is line-terminated so that the peer's readLine() call will return.