TCP和UDP的简单JAVA程序，从《计算机网络 自顶向上方法》中抄的，然后加了点注释

TCP和UDP的简单JAVA程序，从《计算机网络 自顶向下方法》中抄的，然后加了点注释。

以下是按照书打的，加了点注释，也就是我个人的理解，由于我刚出茅庐，而且这方面我感觉蛮难得，希望大家有啥意见提出来，大家一起探讨探讨。

TCP客户端程序代码。

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;


public class TCPClient {

	/**
	 * @param args
	 * @throws Exception 
	 * @throws UnknownHostException 
	 * TCP套接字由，源IP地址，源端口号，目标IP地址，目标端口号组成的。
	 */
	public static void main(String[] args) throws UnknownHostException, Exception {
		// TODO Auto-generated method stub
		String sentence;
		String modifiedSentence;
		BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));	// 获取键盘输入的数据
		Socket clientSocket = new Socket("192.168.1.3", 6789);								// 建立连接时传入IP地址和端口号，TCP是可靠的连接。
		DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
		BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
		sentence = inFromUser.readLine();
		outToServer.writeBytes(sentence + '\n');
		modifiedSentence = inFromServer.readLine();
		System.out.println("From Server: " + modifiedSentence);
		clientSocket.close();
	}

}

TCP服务器端代码

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


public class TCPServer {

	/**
	 * @param args
	 * @throws IOException 
	 */
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		String clientSentence;
		String capitalizedSentence;
		ServerSocket welcomeSocket = new ServerSocket(6789);			//这是一个握手请求，当成功时建立一个可靠连接
		while (true) {
			Socket connectionSocket = welcomeSocket.accept();
			BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
			DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
			clientSentence = inFromClient.readLine();
			capitalizedSentence = clientSentence.toUpperCase() + '\n';
			outToClient.writeBytes(capitalizedSentence);
		}
	}

}

UDP客户端代码

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;


public class UDPClient {

	/**
	 * @param args
	 * @throws IOException 
	 */
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
		DatagramSocket clientSocket = new DatagramSocket();
		InetAddress IPAddress = InetAddress.getByName("192.168.1.3");				
		byte[] sendData = new byte[1024];
		byte[] receiveData = new byte[1024];
		String sentence = inFromUser.readLine();
		sendData = sentence.getBytes();
		DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);		// 与TCP不同，这是无连接的传输，所以把端口号写在packet中，
		clientSocket.send(sendPacket);
		DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
		clientSocket.receive(receivePacket);
		String modifiedSentence = new String(receivePacket.getData());
		System.out.println("From sever:" + modifiedSentence);
		clientSocket.close();
	}

}

UDP服务器端代码

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;


public class UDPServer {

	/**
	 * @param args
	 * @throws IOException 
	 * 
	 * 没有握手请求了。
	 */
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		DatagramSocket serverSocket = new DatagramSocket(9876);
		byte[] receiveData = new byte[1024];
		byte[] sendData = new byte[1024];
		while(true){
			DatagramPacket receivePacket = new DatagramPacket(receiveData,receiveData.length);
			serverSocket.receive(receivePacket);
			String sentence = new String(receivePacket.getData());
			InetAddress IPAddress = receivePacket.getAddress();
			int port = receivePacket.getPort();
			String capitalizedSentence = sentence.toUpperCase();
			sendData = capitalizedSentence.getBytes();
			DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
			serverSocket.send(sendPacket);
		}
	}

}

注释的有点仓促，希望大家多提意见，多多指点，我看到后肯定给答复。