Hello Robyer!
Yep it was the classic steam, and from netlog, the event looks like this:
[19:00:44 1E1C] [STEAM_1] (000000001059CB98:1752) Data received
{
"pollid": 0,
"messages": [
{
"type": "typing",
"timestamp": 236970703,
"utc_timestamp": 1423245626,
"steamid_from": "the_actual_steam_id_goes_here",
"text": ""
}
]
,
"messagelast": 82,
"timestamp": 236970703,
"utc_timestamp": 1423245626,
"messagebase": 81,
"sectimeout": 6,
"error": "OK"
}