Tcp网络编程

客户端程序TcpClient.java：

import java.io.*;
import java.net.*;

public class TcpClient
{
	public static void main(String[] args)
	{
		Socket socket = null;
		DataInputStream in = null;
		DataOutputStream out = null;
		try
		{
			socket = new Socket("127.0.0.1",4331);
			in = new DataInputStream(socket.getInputStream());
			out = new DataOutputStream(socket.getOutputStream());
			char c = 'a';
			while(true)
			{
				if(c > 'z')
					c = 'a';
				out.writeChar(c);
				char s = in.readChar(); // in读取信息，堵塞状态
				System.out.println("客户收到：" + s);
				c++;
				Thread.sleep(500);
			}
		}
		catch (Exception e)
		{
			System.out.println("服务器已断开" + e);
		}
		finally
		{
			try
			{
				if(in != null) in.close();
				if(out != null) out.close();
				if(socket != null) socket.close();
			}
			catch (Exception e)
			{
			}
		}
	}
}

服务器端程序TcpServer.java：

import java.io.*;
import java.net.*;

public class TcpServer
{
	public static void main(String[] args) 
	{
		ServerSocket server = null;
		Socket client = null;
		try
		{
			server = new ServerSocket(4331);
		}
		catch (IOException e)
		{
			System.out.println(e);
		}
		try
		{
			System.out.println("等待客户端呼叫");
			while(true)
			{
				client = server.accept(); // 堵塞状态，除非有客户端呼叫
				System.out.println("新的客户端已建立连接");
				new Server_thread(client).start(); // 为每个客户端启动一个专门的线程
			}
		}
		catch (IOException e)
		{
			System.out.println("正在等待客户端");
		}
		finally
		{
			try
			{
				if(server != null) server.close();
			}
			catch (Exception e)
			{
			}
		}
	}
}

class Server_thread extends Thread
{
	Socket socket;
	DataOutputStream out = null;
	DataInputStream in = null;
	String s = null;
	boolean quesion = false;
	Server_thread(Socket t)
	{
		socket = t;
		try
		{
			out = new DataOutputStream(socket.getOutputStream());
			in = new DataInputStream(socket.getInputStream());
		}
		catch (IOException e)
		{
		}
	}
	public void run()
	{
		try
		{
			while(true)
			{
				char c = in.readChar(); // in读取信息，堵塞状态
				System.out.println("服务器收到：" + c);
				out.writeChar((char)(c-32));
				Thread.sleep(500);
			}
		}
		catch (Exception e)
		{
		}
	}
}

注1：服务器端利用多线程处理客户端
注2：所谓“接收”客户端的套接字连接就是accept()会返回一个和客户端Socket对象相连接的Socket对象，服务器端的这个Socket对象client使用getOutputStream()方法获得的输出流将指向客户端Socket对象socket使用getInputStream()方法获得的那个输入流；同样，服务器端的这个Socket对象client使用getInputStream()方法获得的输入流将指向客户端Socket对象socket使用getOutputStream()方法获得的那个输出流。