/var/log/syslog says this after starting a channel from TVHClient in MX Player and press pause.
Sep 12 19:11:18 rpi tvheadend[501]: htsp: Got connection from 192.168.1.115
Sep 12 19:11:18 rpi tvheadend[501]: htsp: 192.168.1.115: Identified as user 'tvh' (unverified)
Sep 12 19:11:18 rpi tvheadend[501]: htsp: 192.168.1.115 [ tvh ]: Welcomed client software: org.tvheadend.tvhclient (HTSPv23)
Sep 12 19:11:18 rpi tvheadend[501]: htsp: 192.168.1.115 [ tvh | org.tvheadend.tvhclient ]: Identified as user 'tvh'
Sep 12 19:11:18 rpi tvheadend[501]: htsp: 192.168.1.115 [ tvh | org.tvheadend.tvhclient ]: Privileges updated
Sep 12 19:11:31 rpi tvheadend[501]: http: 192.168.1.115: using ticket 2527BC2B215E5FDD47A845C9594AA76649D8336C for /stream/channelid/724101975
Sep 12 19:11:31 rpi tvheadend[501]: mpegts: 12544.75H in Astra - tuning on Montage Technology M88DS3103 : DVB-S #0
Sep 12 19:11:31 rpi tvheadend[501]: subscription: 0315: "HTTP" subscribing on channel "ProSieben", weight: 100, adapter: "Montage Technology M88DS3103 : DVB-S #0", network: "Astra", mux: "12544.75H", provider: "ProSiebenSat.1", service: "ProSieben", profile="pass", hostname="192.168.1.115", username="tvh", client="Mozilla/5.0 (Linux; Android 6.0.1; de-DE; SGP511 Build/23.5.A.1.291) MXPlayer/1.9.5"
Sep 12 19:11:31 rpi tvheadend[501]: linuxdvb: Unable to provide UNC value.
Sep 12 19:11:43 rpi tvheadend[501]: subscription: 0315: "HTTP" unsubscribing from "ProSieben", hostname="192.168.1.115", username="tvh", client="Mozilla/5.0 (Linux; Android 6.0.1; de-DE; SGP511 Build/23.5.A.1.291) MXPlayer/1.9.5"