Tvheadend

Have you looked at https://tvheadend.org/projects/tvheadend/wiki/Htsp ?

Note / follow the links mentioned there:

For information about the HTSP wire format please read HTSMSG binary format

If you're looking to develop a new client, there are several existing client implementations from which you might be able to gain knowledge:

XBMC
Showtime
TVHGuide
PyHTSP (This is a demo client and is WIP, it has limited functionality).

An example in C# should be found here: https://github.com/adamsutton/xbmc-pvr-addons/tree/master/addons/pvr.tvh

I can handle the hello and authenticate now, but I can't find a method to list all available channels (TV-Senders).
How can I get these information?

to list all available channels

Use the "enableAsyncMetadata" method. An "initialSync" will start, which will provide, among other, the available channels via the "channelAdd" reply. You can stop reading the replies once "initialSyncCompleted" is received.

Look at the following Python code, which I use in a script to generate xmltv data (adopted from the PyHTSP demo client). Note that there is a small error in the Wiki HTSP documentation: the reply received is initialSyncCompleted, not initialSyncComplete; "d" is added at the end.

  # Enable async
  args = {}
  if opts.epg:
    args['epg']   = 1
  if opts.update != None:
    args['lastUpdate'] = opts.update
  htsp.enableAsyncMetadata(args)

  # Process messages
  chanNum={}
  chanAdd=[]
  evenAdd=[]
  while True:
    msg = htsp.recv()
    if 'method' in msg:
      if msg['method'] == 'channelAdd':
        chanNum[msg['channelId']]=msg['channelNumber']
        chanAdd.append(msg)    # store 'channelAdd' message
      elif msg['method'] == 'eventAdd':
        msg['channelNumber']=chanNum[msg['channelId']]
        evenAdd.append(msg)    # store 'eventAdd' message
      elif msg['method'] == 'initialSyncCompleted':
        break

Thank you, I tried this already yesterday and get only one or two channelAdd messages in 10min.
Any idea what is the reason for this?

Edit: I attached a 30min communication log

The Channel and Event information I receive in this way is limited to the channels I have mapped and numbered in the TVH web interface.

Generating the xmltv data for the 55 channels I have mapped and 8799 associated epg entries takes about 15 seconds on my rather slow QNAP TS-212 NAS (ARM). It is only about 3 seconds on my Intel i3 notebook.

Another guess, which might influence the results: in https://github.com/adamsutton/tvheadend/blob/master/lib/py/tvh/htsp.py I changed

HTSP_PROTO_VERSION = 6

... mapped and numbered in the TVH web interface.

I have numbered 385 TV and Radio channels. What du you mean with 'mapped'. The TVH-Plugin in XBMC/Kodi shows me all channels.

Generating the xmltv data for the 55 channels I have mapped and 8799 associated epg entries takes about 15 seconds on my rather 
slow QNAP TS-212 NAS (ARM). It is only about 3 seconds on my Intel i3 notebook.

I think its not an performance issue as only a few channel are send regardless the time I let the client run.

Another guess, which might influence the results: in https://github.com/adamsutton/tvheadend/blob/master/lib/py/tvh/htsp.py I changed
[...] to version 17, which my TVH uses.

I tried from 6 to 17 every number - the same result.

... mapped and numbered: once you have done that the channel tab should look like the attached screen shot.

Since the "TVH-Plugin in XBMC/Kodi shows me all channels" it appears you have done that.

Otherwise I have no idea why you are only getting a few channels.

You might want to try the python script I use. I attach it. It will need the "TVH imports" fom here https://github.com/tvheadend/tvheadend/tree/master/lib/py/tvh plus python 2.7.

It looks like a problem in my socket reading code. The data might not processed continuously.
I must rewrite the complete socket stuff which needs some time as I'm a Java developer who tries to write C# code.
Most of my beloved java.nio.* classes must be replaced with C# ones.

Noted. Good luck with the new C# code. I cannot help with C#, being only a hobby programmer.

Out of curiosity: what do you intend to do with your C# HTS client?

I try to write a TVH-plugin for MediaBrowser.