【学习笔记】Java网络编程

Socket 编程

Socket是应用层与TCP/IP协议族通信的中间软件抽象层，它是一组接口。在设计模式中，Socket其实就是一个门面模式，它把复杂的TCP/IP协议族隐藏在Socket接口后面，对用户来说，一组简单的接口就是全部，让Socket去组织数据，以符合指定的协议。可以认为socket=IP+端口。

当连接建立时，服务器会创建一个 Socket 对象。客户端和服务器现在可以通过对 Socket 对象的写入和读取来进行通信。

服务器与客户端进行通信

• 服务器实例化一个 ServerSocket 对象，表示通过服务器上的端口通信。
• 服务器调用 ServerSocket 类的 accept() 方法，该方法将一直等待，直到客户端连接到服务器上给定的端口。
• 服务器正在等待时，一个客户端实例化一个 Socket 对象，指定服务器名称和端口号来请求连接。
• Socket 类的构造函数试图将客户端连接到指定的服务器和端口号。如果通信被建立，则在客户端创建一个 Socket 对象能够与服务器进行通信。
• 在服务器端，accept() 方法返回服务器上一个新的 socket 引用，该 socket 连接到客户端的 socket。

服务器

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketTimeoutException;

public class Server extends Thread {
    private final ServerSocket serverSocket;

    public Server(int port) throws IOException {
        serverSocket = new ServerSocket(port);
        serverSocket.setSoTimeout(10000);
    }

    public void start() {
        while (true) {
            try {
                System.out.println("Waiting for being Connected. Port is " + serverSocket.getLocalPort() + "...");
                Socket server = serverSocket.accept();
                System.out.println("Remote host address is " + server.getRemoteSocketAddress());
                DataInputStream in = new DataInputStream(server.getInputStream());
                System.out.println(in.readUTF());
                DataOutputStream out = new DataOutputStream(server.getOutputStream());
                out.writeUTF(server.getLocalSocketAddress() + " is connected successfully!");
                server.close();
            } catch (SocketTimeoutException s) {
                System.out.println("Socket timed out!");
                break;
            } catch (IOException e) {
                e.printStackTrace();
                break;
            }
        }
    }

    public static void main(String args[]){
        int port = Integer.parseInt(args[0]);
        try {
            Thread thread = new Server(port);
            thread.start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

客户端

public class Client {
    public static void main(String args[]){
        String serverName = args[0];
        int port = Integer.parseInt(args[1]);
        try {
            System.out.println("Connect to the host " + serverName + ", the port is " + port);
            Socket client = new Socket(serverName, port);
            System.out.println("The remote host address is " + client.getRemoteSocketAddress());
            OutputStream outToServer = client.getOutputStream();
            DataOutputStream out = new DataOutputStream(outToServer);

            out.writeUTF("Get data from " + client.getLocalSocketAddress());
            InputStream inFromServer = client.getInputStream();
            DataInputStream in = new DataInputStream(inFromServer);
            System.out.println("The server response is " + in.readUTF());
            client.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

/* 客户端输出
Connect to the host localhost, the port is 6066
The remote host address is localhost/127.0.0.1:6066
The server response is /127.0.0.1:6066 is connected successfully!
*/

/* 服务器输出
Waiting for being Connected. Port is 6066...
Remote host address is /127.0.0.1:63877
Get data from /127.0.0.1:63877
Waiting for being Connected. Port is 6066...
Socket timed out!
*/