• Running MySQL Both the server and the client are essentially a process on the computer
• So the process that the client process sends a request to the server process and gets a response is essentially a Interprocess communication The process
• MySQL Support multiple interprocess communication modes

The process of connecting the client and the server

TCP/IP

• In the real world , The database server process and the client process may run on different hosts , They must communicate with each other through the network
• MySQL use TCP As a network communication protocol between server and client , The client is through IP Address + port To uniquely identify which server to connect to
• By default ,MySQL The server will listen to the local 3306 port

problem ： If 3306 What if the port is occupied ？

• Server side ： stay Start the server when , Can pass -P Specify the port to listen on , For example, the following server monitors 3307：

$ mysqld -P3307

problem ： If the client and server are not on the same host

• Start client Must pass -h The command specifies the IP Address , such as ：

$ mysql -h192.168.0.21 -uroot -P3307 -p

UNIX Domain socket

• If the server and client are on the same host , So you can go through UNIX Domain socket for interprocess communication

How to do the server ？

• After starting the server , The server will listen by default /tmp/sock.sock This domain socket
• If you want to listen to sockets in other domains , You can specify ：

mysqld --socket=/tmp/a.txt

How does the client do ?

• When starting the client , When one of the following three situations occurs ：

  • Do not specify host name
  • Specify the hostname as localhost
  • It specifies --protocol=socket Start parameter of

• The client process will connect to the local directory /tmp/sock.sock.

• If you want to connect to another domain socket ：

mysql -hlocalhost -uroot --socket=/tmp/a.txt -p

Named pipes and shared memory

• windows It also supports communication between server processes and client processes through named pipes

Summary

No matter which way the client and server processes communicate , The final effect is that the client process sends a text to the server process （MySQL sentence ）, After processing, the server process returns a piece of text to the client process （ Processing results ）.

that , What does the server process do with the request sent by the client , To produce the final processing result ？

We will discuss later