TCP connection establishment and closing status and data transmission communication process [including PHP socket API test experiment code]

This article uses PHP code to test a communication process of the TCP transport layer.

TCP/IP Protocol

You can check the details of this protocol by yourself< ;>

PHP’s tcp/udp API content is the content in the PHP manual

socket API

Tested PHP version

TCP connection establishment and closing status and data transmission communication process

PHP code[This is an example in the manual]

 
socket service type
##TCP/IP options file
Then we start the service
Service status viewing command:
netstat -ntlapc The status can be refreshed every second
tcpdump tool:
tcpdump -A -XX -i lo
On the client side, we can use the telent tool to connect and test 
The test diagram is as follows
##Connection and shutdown diagram
If initiated by the client When closed, the status is: 
The client first sends an end message FIN packet, which is in the FIN_WAIT1 state. The server confirms that the response is in the CLOSE_WAIT state. 
The client is in the FIN_WAIT2 state at this time. When the server also sends a FIN end message, the server is in the LAST_LOCK state. After the client confirms, it is in the TIME_WAIT state. The server is closed CLOSED
State transition diagram
The test is the same whether you use the SOCKET API provided by PHP, SWOOLE or C! 
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