一、TCP/IP协议

1、TCP/IP协议包括TCP、IP和UDP等

2、域名通过dns服务器转换为IP地址

3、局域网可以通过IP或者主机地址寻找到相应的主机

4、TCP是可靠的连接，效率低，且连接是一对一，TCP；而UDP是不可靠连接，容易丢失数据，但是效率高，且连接是一对多。

二、端口号

1、端口号唯一确定服务器中的某个应用

2、一台服务器不允许存在两个相同端口号的应用

3、IP：port唯一确定服务器应用程序

4、https的默认端口为443，http为80，https是http的加密和解密的升级版

三、Socket

1、客户端应用程序与Port间使用Socket连接，打个比方，客户端应用程序比作家用电器，Port的IO流比作电流，那么Socket就是插座，家用电器只有将电线插到插座上才能通电

2、服务端与Port间使用ServerSocket连接

3、只要获得了Socket实例，就有了IO流

四、InetAddress类

public class TestTcp {    public static void main(String[] args) {        try {            InetAddress localHost = InetAddress.getLocalHost();            System.out.println(localHost.getHostName());//获取主机名            System.out.println(localHost.getHostAddress());//获取主机地址            localHost = InetAddress.getByName("baidu.com");            System.out.println(localHost.getHostName());            System.out.println(localHost.getHostAddress());        } catch (UnknownHostException e) {            e.printStackTrace();        }    }}

五、简易聊天室

本聊天室包括一个服务端和n个客户端，客户端向服务端发送消息，服务端再将该消息群发给除了它们本身的其它客户端。

想要发消息，必须要拥有IO流，想要IO流就必须拥有Socket，另外有谁的Socket就可以向谁发消息。

聊天室代码如下：

import java.io.*;import java.net.ServerSocket;import java.net.Socket;import java.util.ArrayList;import java.util.List;import java.util.Scanner;public class TalkTool {}//服务端class ServerT{    public static void main(String[] args) {        try {            ServerSocket serverSocket = new ServerSocket(9014);//建立服务端套接字与端口关联            System.out.println("服务端启动成功，等待客户端连接");            List
    
      socketList = new ArrayList<>();            while (true) {                //主线程只负责客户端连接                Socket socket = serverSocket.accept();//等待客户端连接(阻塞状态)                System.out.println("有客户端连入");                socketList.add(socket);                new Thread(new ForwardT(socket,socketList)).start();            }        } catch (IOException e) {            e.printStackTrace();        }    }}//客户端class ClientT{    public static void main(String[] args) {        try {            Socket socket = new Socket("192.168.226.1",9014);//建立连接,IP地址根据实际情况设置            System.out.println("客户端与服务端建立了连接");            OutputStream outputStream = socket.getOutputStream();            PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(outputStream),true);            Scanner scanner = new Scanner(System.in);            //独立线程负责接收消息            new Thread(new ReceveT(socket)).start();            while (true) {                printWriter.println(scanner.next());            }        } catch (IOException e) {            e.printStackTrace();        }    }}//服务端转发线程class ForwardT implements Runnable{    private Socket socket;    private List
     
       socketList;    public ForwardT(Socket socket,List
      
       socketList){        this.socket=socket;        this.socketList=socketList;    }    @Override    public void run() {        try {            while (true) {                InputStream inputStream = socket.getInputStream();                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));                String msg = bufferedReader.readLine();                System.out.println(msg);                for (Socket sk:socketList                     ) {                    if (sk!=socket){//把自己排除掉                    //发送给其它客户端，必须要有其它客户端的Socket                        OutputStream outputStream = sk.getOutputStream();                        PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(outputStream),true);                        printWriter.println(socket+"说:"+msg);                    }                }            }        } catch (IOException e) {            e.printStackTrace();        }    }}//客户端接收线程class ReceveT implements Runnable{    private Socket socket;    public ReceveT(Socket socket){        this.socket=socket;    }    @Override    public void run() {        try {            while (true) {                InputStream inputStream = socket.getInputStream();                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));                System.out.println("服务端返回"+bufferedReader.readLine());            }        } catch (IOException e) {            e.printStackTrace();        }    }}