Java 套接字编程 - 套接字服务器、客户端示例

欢迎来到 Java Socket 编程示例。每个服务器都是在特定系统上运行并侦听特定端口的程序。套接字绑定到端口号，当我们运行任何服务器时，它只会侦听套接字并等待客户端请求。例如，在端口 8080 上运行的 tomcat 服务器等待客户端请求，一旦收到任何客户端请求，它就会响应它们。

Java 套接字编程

套接字是网络上运行的两个程序之间的双向通信链路的一个端点。套接字绑定到端口号，以便 TCP 层可以识别要发送数据的应用程序。在 Java 套接字编程示例教程中，我们将学习如何编写Java 套接字服务器和Java 套接字客户端程序。我们还将学习服务器客户端程序如何在套接字上读取和写入数据。java.net.Socket和java.net.ServerSocket是实现 Socket 和 Socket 服务器的 Java 类。

Java 套接字服务器示例

package com.journaldev.socket;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ClassNotFoundException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * This class implements java Socket server
 * @author pankaj
 *
 */
public class SocketServerExample {

    //static ServerSocket variable
    private static ServerSocket server;
    //socket server port on which it will listen
    private static int port = 9876;

    public static void main(String args[]) throws IOException, ClassNotFoundException{
        //create the socket server object
        server = new ServerSocket(port);
        //keep listens indefinitely until receives 'exit' call or program terminates
        while(true){
            System.out.println("Waiting for the client request");
            //creating socket and waiting for client connection
            Socket socket = server.accept();
            //read from socket to ObjectInputStream object
            ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
            //convert ObjectInputStream object to String
            String message = (String) ois.readObject();
            System.out.println("Message Received: " + message);
            //create ObjectOutputStream object
            ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
            //write object to Socket
            oos.writeObject("Hi Client "+message);
            //close resources
            ois.close();
            oos.close();
            socket.close();
            //terminate the server if client sends exit request
            if(message.equalsIgnoreCase("exit")) break;
        }
        System.out.println("Shutting down Socket server!!");
        //close the ServerSocket object
        server.close();
    }

}

Java 套接字客户端

package com.journaldev.socket;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

/**
 * This class implements java socket client
 * @author pankaj
 *
 */
public class SocketClientExample {

    public static void main(String[] args) throws UnknownHostException, IOException, ClassNotFoundException, InterruptedException{
        //get the localhost IP address, if server is running on some other IP, you need to use that
        InetAddress host = InetAddress.getLocalHost();
        Socket socket = null;
        ObjectOutputStream oos = null;
        ObjectInputStream ois = null;
        for(int i=0; i<5;i++){
            //establish socket connection to server
            socket = new Socket(host.getHostName(), 9876);
            //write to socket using ObjectOutputStream
            oos = new ObjectOutputStream(socket.getOutputStream());
            System.out.println("Sending request to Socket Server");
            if(i==4)oos.writeObject("exit");
            else oos.writeObject(""+i);
            //read the server response message
            ois = new ObjectInputStream(socket.getInputStream());
            String message = (String) ois.readObject();
            System.out.println("Message: " + message);
            //close resources
            ois.close();
            oos.close();
            Thread.sleep(100);
        }
    }
}

要测试服务器-客户端通信的 Java 套接字编程，首先我们需要运行SocketServerExample类。当您运行套接字服务器时，它只会打印“等待客户端请求”，然后等待客户端请求。现在，当您运行 SocketClientExample 类时，它将向 Java 套接字服务器发送请求并将响应消息打印到控制台。这是 Java 套接字服务器程序的输出SocketServerExample。

Waiting for the client request
Message Received: 0
Waiting for the client request
Message Received: 1
Waiting for the client request
Message Received: 2
Waiting for the client request
Message Received: 3
Waiting for the client request
Message Received: exit
Shutting down Socket server!!

以下是 Java 套接字客户端程序的输出SocketClientExample。

Sending request to Socket Server
Message: Hi Client 0
Sending request to Socket Server
Message: Hi Client 1
Sending request to Socket Server
Message: Hi Client 2
Sending request to Socket Server
Message: Hi Client 3
Sending request to Socket Server
Message: Hi Client exit

这就是 Java 中 Socket 编程的快速总结。希望您能够开始使用 Java Socket 服务器和 Java Socket 客户端编程。参考：Oracle Doc