运输层协议----UDP

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

class UDPClient
{
	public static void main(String[] args) throws IOException
	{
		// 构造数据报套接字并将其绑定到本地主机上任何可用的端口
		DatagramSocket client = new DatagramSocket();
		// 在给定主机名的情况下确定主机的 IP 地址
		InetAddress addr = InetAddress.getByName("127.0.0.1");
		int port = 10021;
		for (int i = 0; i < 5; i++)
		{
			String sendStr = "Hello! I‘m Client" + i;
			byte[] sendBuf = sendStr.getBytes();

			// 构造数据报包，用来将长度为 length 的包发送到指定主机上的指定端口号。length 参数必须小于等于 buf.length。
			// buf - 包数据 length - 包长度 address - 目的地址 port - 目的端口号
			DatagramPacket sendPacket = new DatagramPacket(sendBuf, sendBuf.length, addr, port);

			// 从此套接字发送数据报包。DatagramPacket 包含的信息指示：将要发送的数据、其长度、远程主机的 IP
			// 地址和远程主机的端口号。
			client.send(sendPacket);

			byte[] recvBuf = new byte[100];

			// 构造 DatagramPacket，用来接收长度为 length 的数据包。 length 参数必须小于等于
			// buf.length。
			DatagramPacket recvPacket = new DatagramPacket(recvBuf, recvBuf.length);

			// 从此套接字接收数据报包。
			client.receive(recvPacket);
			String recvStr = new String(recvPacket.getData(), 0, recvPacket.getLength());
			System.out.println("recvMsg =" + recvStr +"; remotePort =" + recvPacket.getPort());
		}

		client.close();
	}
}

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

class UDPServer
{
	public static void main(String[] args) throws IOException
	{
		DatagramSocket server = new DatagramSocket(10021);
		byte[] recvBuf = new byte[100];
		for (int i = 0; i < 5; i++)
		{
			DatagramPacket recvPacket = new DatagramPacket(recvBuf, recvBuf.length);
			server.receive(recvPacket);
			String recvStr = new String(recvPacket.getData(), 0, recvPacket.getLength());
			int port = recvPacket.getPort();
			System.out.println("reveMsg = "+ recvStr + "; remote port =" + port);

			InetAddress addr = recvPacket.getAddress();
			String sendStr = "Hello ! I‘m Server" + i;

			byte[] sendBuf = sendStr.getBytes();
			DatagramPacket sendPacket = new DatagramPacket(sendBuf, sendBuf.length, addr, port);

			server.send(sendPacket);
		}

		server.close();
	}
}

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;

class TCPClient
{
	public static void main(String[] args) throws IOException
	{
		// 构造数据报套接字并将其绑定到本地主机上任何可用的端口
		Socket client = new Socket();
		// 在给定主机名的情况下确定主机的 IP 地址
		InetAddress addr = InetAddress.getByName("127.0.0.1");
		int port = 10021;
		client.connect(new InetSocketAddress(addr, port));
		OutputStream output = client.getOutputStream();
		InputStream input = client.getInputStream();
		for (int i = 0; i < 5; i++)
		{
			String sendStr = "Hello! I‘m Client" + i;

			output.write(sendStr.getBytes());

			byte[] recvBuf = new byte[100];


			int length = input.read(recvBuf);
			String str = new String(recvBuf);
			System.out.println("recvMsg =" + str.substring(0,length));
		}

		client.close();
	}
}

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

class TCPServer
{
	public static void main(String[] args) throws IOException
	{
		ServerSocket server = new ServerSocket(10021);
		Socket socket = server.accept();
		OutputStream output = socket.getOutputStream();
		InputStream input = socket.getInputStream();
		byte[] recvBuf = new byte[100];
		for (int i = 0; i < 5; i++)
		{
			int len = input.read(recvBuf);
			String str = new String(recvBuf);
			
			System.out.println("reveMsg = "+ str.substring(0,len) + "; remote port =" + socket.getRemoteSocketAddress());

			String sendStr = "Hello ! I‘m Server" + i;

            
			output.write(sendStr.getBytes());
		}

		server.close();
	}
}