It's as easy as connection with a TCP client @ port 8000 and sending a string
To subscribe a decoder to an encoder:?
CMD=START&UNIT.ID=ALL&STREAM.HOST=10.100.1.42&VW.ACTIVE=FALSE&STREAM.CONNECT=TRUE&CMD=END
To use the serial port on a decoder you would connect a TCP client @ port 6752, it's like opening a port directly to the device, just send the raw device protocol commands.
Matt