tcp实现聊天

客户端

package inet;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;

//用户端
public class TcpClientDemo1 {
    public static void main(String[] args) {

        Socket socket=null;
        OutputStream os=null;


        try {
            //1.要知道服务器的地址和端口号
            InetAddress serverIP=InetAddress.getByName("127.0.0.1");
            int port=9999;
            //2.创建一个socket连接
            socket =new Socket(serverIP,port);
            //3.发送消息io流
            os=socket.getOutputStream();
            os.write("你好!!!".getBytes());

        } catch (Exception e) {
            e.printStackTrace();
        }finally{

            if (os!=null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }


        }

    }
}

if (os!=null)--->直接关闭一个空指针会产生异常，因此要判断；如果值为null并不是说他已经被关闭了，而是没有正确赋值，例如丢包什么的

服务端

package inet;

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

//客户端
public class TcpServerDemo1 {
    public static void main(String[] args) {

        ServerSocket serverSocket=null;
        Socket socket=null;
        InputStream is=null;
        ByteArrayOutputStream baos=null;

        try {
            //1.我得有一个地址
            serverSocket = new ServerSocket(9999);
            //2.等待客户端连接过来
            socket=serverSocket.accept();
            //3.读取客户端消息
            is=socket.getInputStream();

            //管道流
            baos = new ByteArrayOutputStream();
            byte[] buffer=new byte[1024];
            int len;
            while((len= is.read(buffer))!=-1){
                baos.write(buffer,0,len);
            }
            System.out.println(baos.toString());

        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if (baos!=null){
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (is!=null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (serverSocket!=null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }


        }
    }
}