网络编程是现代软件开发中不可或缺的一部分，它使得我们能够通过网络连接和交互，实现数据传输和通信。Java作为一种广泛应用于网络编程的编程语言，提供了丰富的库和工具，使得开发者能够轻松地构建强大的网络应用程序。本文将详细介绍Java网络编程的基础知识，包括套接字、TCP和UDP协议、客户端和服务器端编程等，并提供相关示例代码，帮助读者快速上手。
一、套接字(Socket)：连接的基石
在Java网络编程中，套接字(Socket)是实现网络通信的基本构建块。套接字提供了一种机制，使得不同主机上的进程能够通过网络进行通信。Java提供了java.net包，其中的Socket类和ServerSocket类分别用于客户端和服务器端的套接字编程。
示例代码：
// 客户端代码
import java.io.*;
import java.net.*;public class Client {public static void main(String[] args) {try {Socket socket = new Socket("服务器IP地址", 12345);// 发送数据OutputStream outputStream = socket.getOutputStream();PrintWriter writer = new PrintWriter(outputStream);writer.println("Hello, Server!");writer.flush();// 接收数据InputStream inputStream = socket.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));String response = reader.readLine();System.out.println("Server response: " + response);// 关闭连接socket.close();} catch (IOException e) {e.printStackTrace();}}
}// 服务器端代码
import java.io.*;
import java.net.*;public class Server {public static void main(String[] args) {try {ServerSocket serverSocket = new ServerSocket(12345);System.out.println("Server started, waiting for client...");Socket socket = serverSocket.accept();System.out.println("Client connected.");// 接收数据InputStream inputStream = socket.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));String request = reader.readLine();System.out.println("Client request: " + request);// 发送数据OutputStream outputStream = socket.getOutputStream();PrintWriter writer = new PrintWriter(outputStream);writer.println("Hello, Client!");writer.flush();// 关闭连接socket.close();serverSocket.close();} catch (IOException e) {e.printStackTrace();}}
}
二、TCP和UDP协议：可靠与高效之间的抉择
在网络编程中，TCP和UDP是两种常用的传输协议。TCP协议提供可靠的、面向连接的数据传输，而UDP协议则提供不可靠的、无连接的数据传输。Java网络编程中可以使用Socket和ServerSocket类来实现TCP协议的通信，使用DatagramSocket和DatagramPacket类来实现UDP协议的通信。
TCP通信示例代码：
// TCP客户端代码
import java.io.*;
import java.net.*;public class TCPClient {public static void main(String[] args) {try {Socket socket = new Socket("服务器IP地址", 12345);// 发送数据OutputStream outputStream = socket.getOutputStream();PrintWriter writer = new PrintWriter(outputStream);writer.println("Hello, Server!");writer.flush();// 接收数据InputStream inputStream = socket.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));String response = reader.readLine();System.out.println("Server response: " + response);// 关闭连接socket.close();} catch (IOException e) {e.printStackTrace();}}
}
// TCP服务器端代码
import java.io.*;
import java.net.*;public class TCPServer {public static void main(String[] args) {try {ServerSocket serverSocket = new ServerSocket(12345);System.out.println("Server started, waiting for client...");Socket socket = serverSocket.accept();System.out.println("Client connected.");// 接收数据InputStream inputStream = socket.getInputStream();BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));String request = reader.readLine();System.out.println("Client request: " + request);// 发送数据OutputStream outputStream = socket.getOutputStream();PrintWriter writer = new PrintWriter(outputStream);writer.println("Hello, Client!");writer.flush();// 关闭连接socket.close();serverSocket.close();} catch (IOException e) {e.printStackTrace();}}
}
UDP通信示例代码：
// UDP客户端代码
import java.io.*;
import java.net.*;public class UDPClient {public static void main(String[] args) {try {DatagramSocket socket = new DatagramSocket();// 发送数据String message = "Hello, Server!";byte[] sendData = message.getBytes();InetAddress serverAddress = InetAddress.getByName("服务器IP地址");DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, serverAddress, 12345);socket.send(sendPacket);// 接收数据byte[] receiveData = new byte[1024];DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);socket.receive(receivePacket);String response = new String(receivePacket.getData(), 0, receivePacket.getLength());System.out.println("Server response: " + response);// 关闭连接socket.close();} catch (IOException e) {e.printStackTrace();}}
}
// UDP服务器端代码
import java.io.*;
import java.net.*;public class UDPServer {public static void main(String[] args) {try {DatagramSocket socket = new DatagramSocket(12345);System.out.println("Server started, waiting for client...");// 接收数据byte[] receiveData = new byte[1024];DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);socket.receive(receivePacket);String request = new String(receivePacket.getData(), 0, receivePacket.getLength());System.out.println("Client request: " + request);// 发送数据String message = "Hello, Client!";byte[] sendData = message.getBytes();InetAddress clientAddress = receivePacket.getAddress();int clientPort = receivePacket.getPort();DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, clientAddress, clientPort);socket.send(sendPacket);// 关闭连接socket.close();} catch (IOException e) {e.printStackTrace();}}
}
