java - 在单个系统上运行客户端/服务器程序

Question

我想知道是否有两个程序，一个称为服务器，另一个称为客户端，这两个程序分别说明服务器和客户端，是否可以在一台机器上测试它们？考虑到我定义了客户端套接字如下:

socket = new Socket("127.0.0.1",3000);

编辑: 服务器部分:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

class TCPServer
{
       private static ServerSocket serverSocket;
        private static Socket socket;
        private static PrintWriter toClient;
        private static BufferedReader fromClient;
        public static void run() throws IOException
            {
            System.out.println("Server is waiting for connections...");
            while (true)
            {
                openStreams();
                processClient();
                closeStreams();
            }

        }

        public static void openStreams() throws IOException
            {
            serverSocket = new ServerSocket(3000);
            socket = serverSocket.accept();
            toClient = new PrintWriter(socket.getOutputStream(),true);
            fromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        }
        public static void closeStreams() throws IOException
            {
            fromClient.close();
            toClient.close();
            socket.close();
            serverSocket.close();
        }
      public static void processClient()throws IOException
{
    String msg = null;
    do {
        msg = fromClient.readLine();
        toClient.println("Client said " + msg);
    } while (!"exit".equals(msg));
}

        }

客户端部分:

package clientserver.pkg1;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

class TCPClient
{
      private PrintWriter toServer;
            private BufferedReader fromServer;
            private Socket socket;
            public void Client( )throws IOException
                {
                socket = new Socket("127.0.0.1",3000);
            }
            public void openStreams() throws IOException
         {

                toServer = new PrintWriter(socket.getOutputStream(),true);
                fromServer = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            }
            public void closeStreams() throws IOException
                {
                fromServer.close();
                toServer.close();
                socket.close();
            }
          public void run()throws IOException
{
    openStreams();
    String msg = "";
    Scanner scanner = new Scanner(System.in);
    while (!"exit".equals(msg))
    {
        System.out.print(">");
        msg = scanner.nextLine();
        toServer.println(msg);
        String tmp = fromServer.readLine();
        System.out.println("Server said: " + tmp);
    }
    closeStreams();
}

            }

主类

public static void main(String[] args) {

       try
            {
                 TCPServer server = new TCPServer() {};
                 TCPClient client = new TCPClient();
                 client.run();
                 server.run();




            }
            catch(IOException e)
            {
                 System.err.println("Error in Client " + e.getMessage());
            }




java.lang.NullPointerException

1

toServer = new PrintWriter(socket.getOutputStream(),true);

2

      public void run()throws IOException
{
    openStreams();
.....
}

3

 public static void main(String[] args) {

       try
            {
                 TCPClient client = new TCPClient();
                 client.run();
            }

在client.run();

Answer 1

是的，你可以编写这样的程序。有一个useful tutorial for this 。 简而言之，这一切都归结为准备一个 ServerSocket:

ServerSocket createSocket() {
    ServerSocket serverSocket;
    try {
        serverSocket = new ServerSocket(3000);
    } catch (IOException ex) {
        ex.printStackTrace(System.err);
        throw ex;
    }
    return serverSocket;
}

从程序员的角度来看，驻留在远程计算机上的服务器和驻留在本地计算机上的服务器没有区别。

您可以尝试编写两个不同的程序，一个用于服务器，一个用于客户端。 这是客户端的主要内容:

public static void main(String[] args) {
  try {
      TCPClient client = new TCPClient() {};
      client.run();
  } catch(IOException e) {
    System.err.println("Error in Client " + e.getMessage());
  }

这对于服务器来说:

public static void main(String[] args) {
  try {
      TCPServer server = new TCPServer() {};
      server.run();
  } catch(IOException e) {
    System.err.println("Error in Server " + e.getMessage());
  }

然后先运行服务器，然后在不同的控制台中运行客户端。