Divide udp_port parameter into transport_protocol and stream_port

[tbolin]

Suggestion: Divide the udp_port argument into two arguments. The transport protocol would be set by transport_protocol,
a string that should be either UDP or TCP, and the port should be set by stream_port, an integer.

Motivation: Currently, the udp_port parameter decides both if TCP or UDP is used, and which port that is used. The port is however only selectable for UDP. If TCP is used, the port is always random. Specifying which TCP port that should be used could be useful.
The current parameter name is also misleading.