After the connection is marked as needing keepalive, the final data is sent and the first keepalive probe packet interval.
Default value: 2hours.
The number of times a keepalive probe packet is sent before a decision is made to notify the application layer of the connection being broken.
Default value: 9.
After the KeepAlive probe packet has started, the probe packet is sent once every few hours.
Default value: 75s
According to the above parameters, if a client sent a packet marked as keepalive, if disconnected, the server needs to 7200s+9*75s=7875s, the connection will be released.