Persistence from single IP address

You could try something like this:

when CLIENT_ACCEPTED {
    set src_IP [IP::client_addr]
    if { [session lookup uie $src_IP] equals "" } {
      session add uie $src_IP [TCP::remote_port] 1800
      log local0. "added client port [session lookup uie $src_IP] for client ip $src_IP "
    } else {
      log local0. "existing client port [session lookup uie $src_IP] for client ip $src_IP"
    }
}

The 1800 is time in seconds you want to keep the persistence record in the session table. The logging statements are for debugging/testing purposes, you can yank them after your testing is complete, or just comment them out.