Port 119: NNTP
Port 119 is NNTP, the protocol for reading and posting to Usenet newsgroups.
What runs on port 119
News servers listen on TCP 119 for newsreaders and for exchanging articles with other servers. The encrypted version runs on 563. Usenet is much quieter than it once was but is still used, mostly through paid providers for binary downloads.
On a home network
Home devices do not listen on 119. Download tools like SABnzbd, sometimes run on a NAS, connect out to Usenet providers, usually on 563 or 443.
If port 119 is reachable from the internet
A news server on a home connection would be unusual. If something answers on 119 from outside, find out what it is; an open server that accepts posts from anyone would be abused for spam.
How to check whether it is open on your network
There is normally nothing to check at home. An outside scan of your public address should show 119 closed.
To find out whether port 119 is open on something in your home, and whether the internet can reach it, the app scans your Wi-Fi from your phone and checks your public address from the outside. It says what it checked and what it could not. Get RECON for iPhone — one-time purchase, no account, nothing leaves the device.