How to get active connections from iControlREST API

You need to use query parameters. Here are the specific fields you can use:

  age             Specifies the age, in seconds, of a connection
  connection-id
  cs-client-addr  Specifies the clientside remote address of the active connections
  cs-client-port  Specifies the clientside remote port of the active connections
  cs-server-addr  Specifies the clientside local address of the active connections
  cs-server-port  Specifies the clientside local port of the active connections
  protocol        Specifies the protocol used for specified connections (for example: tcp, udp)
  ss-client-addr  Specifies the serverside local address of the active connections
  ss-client-port  Specifies the serverside local port of the active connections
  ss-server-addr  Specifies the serverside remote address of the active connections
  ss-server-port  Specifies the serverside remote port of the active connections
  type            Specifies the connnection type used for specified connections (for example: any, mirror, self)

So to build the URL for all connections to my 192.168.102.50:80 virtual, it would look like this:

https://172.16.44.128/mgmt/tm/sys/connection?options=cs-server-addr+192.168.102.50+cs-server-port+80

And the returned json is:

{"kind":"tm:sys:connection:connectionstats","selfLink":"https://localhost/mgmt/tm/sys/connection?options=cs-server-addr+192.168.102.50+cs-server-port+80&ver=11.6.0","apiRawValues":{"apiAnonymous":"Sys::Connections\n192.168.102.1:55264  192.168.102.50:80  192.168.102.1:55264  192.168.103.11:80    tcp  3  (tmm: 0)  none\n192.168.102.1:55262  192.168.102.50:80  192.168.102.1:55262  192.168.103.11:8080  tcp  1  (tmm: 0)  none\n192.168.102.1:55266  192.168.102.50:80  192.168.102.1:55266  192.168.103.10:8080  tcp  2  (tmm: 0)  none\n192.168.102.1:55263  192.168.102.50:80  192.168.102.1:55263  192.168.103.10:80    tcp  1  (tmm: 1)  none\n192.168.102.1:55261  192.168.102.50:80  192.168.102.1:55261  192.168.103.10:8080  tcp  1  (tmm: 1)  none\n192.168.102.1:55265  192.168.102.50:80  192.168.102.1:55265  192.168.103.11:8080  tcp  2  (tmm: 1)  none\nTotal records returned: 6\n"}}