[Xymon] no client results arrive, lot of TIME_WAIT at server

experts,

i have a new (not my first) Xymon installation (4.3.28 on RH 7.4, self compiled). All looks good, but the clients only show the network tests (conn, ssh). Only the Xymon server itself shows everything (disk, cpu,...).

• all clients are RH 7.4, same install image used (i just copied over the client part with client config, create a cronjob for automatic start, so no root access nor extra install needed)
• nothing suspicious in server or client logs (even in debug mode)
• no ghosts
• if i send a test manually (the old BB way) this shows at Xymon immediately (so the client settings are ok)
• if i shutdown the xymond at server, the client logs complains:

2017-10-19 05:09:18.051994 Whoops ! Failed to send message (Connection failed) 2017-10-19 05:09:18.052104 -> Could not connect to Xymon daemon at 10.137.56.43:1984 (Connection refused)

(so obviously they communicate)

Querying the xymond shows: xymon 127.0.0.1 "query clientname.ssh" green <!-- [flags:OrdastLe] --> Thu Oct 19 05:21:29 2017 ssh ok is ok, but xymon 127.0.0.1 "query clientname.disk" shows nothing

Any ideas?

Norbert