Java Socket TCP/UDP

Java Socket实例

说明 - ServerSocket为阻塞式监听，可换用非阻塞式、性能更好的NIO ServerSocketChannel。

package main;

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

public class Main {

    public static void main(String[] args) {
        new Thread(Main::serverSocket).start();

        System.out.println("Please input:");
        try (var s = new Socket("127.0.0.1", 12345);
                var out = new PrintWriter(s.getOutputStream(), true);
                // 接数据最好在新线程中，避免收发互斥。
                var in = new BufferedReader(new InputStreamReader(s.getInputStream()));
                var stdIn = new BufferedReader(new InputStreamReader(System.in))) {
            String userInput;
            while ((userInput = stdIn.readLine()) != null) {
                out.println(userInput);
                System.out.println("Echo: " + in.readLine());
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }

    public static void serverSocket() {
        try (var ss = new ServerSocket(12345); var s = ss.accept();
                var out = new PrintWriter(s.getOutputStream(), true);
                var in = new BufferedReader(new InputStreamReader(s.getInputStream()))) {
            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                out.println(inputLine);
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }
}

Socket客户端新线程中接受数据

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class SocketClient {

    private OutputStreamWriter out;

    public SocketClient(String ip, int port) {
        try {
            var socket = new Socket(ip, port);
            out = new OutputStreamWriter(socket.getOutputStream());
            new Thread(() -> {
                try {
                    var in = new InputStreamReader(socket.getInputStream());
                    while (true) {
                        try {
                            if (socket.isClosed()) {
                                return;
                            }
                            int len;
                            while ((len = in.read()) != -1) {
                                System.out.println((char) len);
                            }
                        } catch (IOException ex) {
                            System.err.println(ex);
                        }
                    }
                } catch (IOException ex) {
                    System.err.println(ex);
                }
            }).start();
        } catch (UnknownHostException ex) {
            System.err.println(ex);
        } catch (IOException ex) {
            System.err.println(ex);
        }
    }

    public void sendMessage(String msg) {
        try {
            out.write(msg);
            out.flush();
        } catch (IOException ex) {
            System.err.println(ex);
        }
    }

    public static void main(String[] args) {
        SocketClient sc = new SocketClient("192.168.3.55", 8282);
        System.out.println("new SocketClient...");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            System.err.println(ex);
        }
        sc.sendMessage("a1");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            System.err.println(ex);
        }
        sc.sendMessage("b1");
    }
}

非控制台方式收发 Socket：
  while (true) {
    byte[] buf = new byte[1024];
    var packet = new DatagramPacket(buf, buf.length);
    socket.receive(packet);
    var rMsg = packet.getAddress() + ":" + packet.getPort() + " says: " + new String(packet.getData(), 0, packet.getLength());
    System.out.println(rMsg);
  }

    final DatagramSocket socket = client.getDatagramSocket();
    System.out.println("getDatagramSocket getInetAddress - " + socket.getInetAddress());
    final SocketAddress remoteAddress = client.getRemotePeerSocketAddress();
    System.out.println("send reply - " + socket.toString());
    byte[] buf = "reply.".getBytes();
    DatagramPacket packet = new DatagramPacket(buf, buf.length);
    packet.setSocketAddress(remoteAddress);
    socket.send(packet);