Tcp/ip protocol

Socket

1. What is a server ？

A set of software that provides external services , Put it on the Internet （IP Address ）

1. What is a client ？

   It is a software for connecting to the server

3. TCP/IP What is the agreement ？

    It can realize information transmission between multiple different networks

1. Network programming 3 elements

   1. agreement

   2. IP Address

      1. LAN IP Address

      2. Public network IP Address （ Bought ）

      3. View this machine IP operation

         ipconfig    

         ping 192.168.17.38

         request timeout ： Unable to connect

         68ms: Can be connected

         4.   special IP Address 
                    1.   Local return address (hostAddress)：`127.0.0.1`  
                    2.   Host name (hostName)：`localhost`

         1. domain name 、

         2. Port number

            Port number ： An integer in two bytes , Its value range is 0~65535.

             1.  Recognized port ：0~1023. Occupied by predefined service communication , Such as ：HTTP（80）,FTP（21）,Telnet（23）
             2.  Registered port ：1024~49151. Assign to a user process or application . Such as ：Tomcat（8080）,MySQL（3306）,Oracle（1521）.
             3.  dynamic /  Private port ：49152~65535.