Ok, so this is the result:
[yves@localhost ~]$ sudo -u tvheadend /usr/bin/tvheadend -p /var/run/tvheadend.pid -c /var/lib/tvheadend/config -6 -C --http_port 9981 --htsp_port 9982
2017-01-26 21:51:08.002 [ INFO] main: Log started
2017-01-26 21:51:08.023 [ INFO] config: loaded
2017-01-26 21:51:08.495 [ INFO] scanfile: DVB-T - loaded 43 regions with 1107 networks
2017-01-26 21:51:08.496 [ INFO] scanfile: DVB-S - loaded 1 regions with 112 networks
2017-01-26 21:51:08.496 [ INFO] scanfile: DVB-C - loaded 17 regions with 56 networks
2017-01-26 21:51:08.496 [ INFO] scanfile: ATSC - loaded 2 regions with 14 networks
2017-01-26 21:51:10.909 [ INFO] dvr: Creating new configuration ''
2017-01-26 21:51:10.910 [ INFO] CSA: Using SSE2 128bit parallel descrambling
2017-01-26 21:51:10.910 [ INFO] epggrab: module eit created
2017-01-26 21:51:10.910 [ INFO] epggrab: module uk_freesat created
2017-01-26 21:51:10.910 [ INFO] epggrab: module uk_freeview created
2017-01-26 21:51:10.910 [ INFO] epggrab: module viasat_baltic created
2017-01-26 21:51:10.915 [ ERROR] upnp: upnp_thread_unicast - failed to create socket [Address family not supported by protocol]
2017-01-26 21:51:10.921 [ INFO] epggrab: module opentv-skyit created
2017-01-26 21:51:10.922 [ INFO] epggrab: module opentv-ausat created
2017-01-26 21:51:10.922 [ INFO] epggrab: module opentv-skyuk created
2017-01-26 21:51:10.922 [ INFO] epggrab: module opentv-skynz created
2017-01-26 21:51:10.929 [ INFO] epggrab: module pyepg created
2017-01-26 21:51:10.929 [ INFO] epggrab: module xmltv created
2017-01-26 21:51:10.941 [ INFO] epgdb: loaded v2
2017-01-26 21:51:10.941 [ INFO] epgdb: config 1
2017-01-26 21:51:10.941 [ INFO] epgdb: channels 0
2017-01-26 21:51:10.941 [ INFO] epgdb: brands 0
2017-01-26 21:51:10.941 [ INFO] epgdb: seasons 0
2017-01-26 21:51:10.941 [ INFO] epgdb: episodes 0
2017-01-26 21:51:10.941 [ INFO] epgdb: broadcasts 0
2017-01-26 21:51:10.942 [ NOTICE] START: HTS Tvheadend version 4.0.9 started, running as PID:2283 UID:966 GID:39, CWD:/home/yves CNF:/var/lib/tvheadend/config
2017-01-26 21:51:11.735 [ INFO] AVAHI: Service 'Tvheadend' successfully established.
Still not listening on port 9981:
[yves@localhost ~]$ netstat -ltn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:3050 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:6379 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:17434 0.0.0.0:* LISTEN
