~$ curl -v -H 'Content-Type: application/json' --data '{"a": 1, "b": 2}' http://localhost:65451/cgi-bin/1.pl
*   Trying ::1...
* TCP_NODELAY set
* Connection failed
* connect to ::1 port 65451 failed: Connection refused
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 65451 (#0)
> POST /cgi-bin/1.pl HTTP/1.1
> Host: localhost:65451
> User-Agent: curl/7.58.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 16
> 
* upload completely sent off: 16 out of 16 bytes

==== Hangs here for about 5 sseconds =======

< HTTP/1.1 504 Gateway Time-out
< Date: Fri, 09 Mar 2018 14:40:55 GMT
< Content-Type: text/html
< Server: inets/6.4.5
* no chunk, no close, no size. Assume close to signal end
< 
* Closing connection 0
~$