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();

	}

}