Wrk close connection so quickly, what is the condition to make wrk close connection?

[tantm3]

Hi everyone!

I am faced with the issue that the work tool opens and closes the connection so fast even though we have the keep-alive option enabled.
I checked the established connection with the command netstat, here is the output:

netstat -tn | grep 163 | grep ES
tcp        0    859 49.213.85.162:80        49.213.85.163:6478      ESTABLISHED
tcp        0    859 49.213.85.162:80        49.213.85.163:6520      ESTABLISHED

I saw that source ports: "6478" and "6520" from wrk server are changed continuously.
I run test from server with IP 49.213.85.163 and use this command: ./wrk -t1 -c2 -d300s http://49.213.85.162
It seems like the wrk tool is send a fix amount of HTTP requests (in my case about 100request/s)and then it will renew a connection.
So, what is the condition that makes the wrk close the connection and can I increase the connection time from wrk so that it's not established a new connection?

Thanks for your time reading my question!