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Port 4937 (atsc-mh-ssc)

IANA assigns port 4937 to atsc-mh-ssc: ATSC-M/H Service Signaling Channel.

Registered (user) port, 1024-49151 UDP

Port 4937 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
atsc-mh-ssc UDP ATSC-M/H Service Signaling Channel Jerry Whitaker -

Registry dates for this port: registered 2008-10-27.

Check what is listening on port 4937

Linux: UDP 4937
sudo ss -ulnp 'sport = :4937'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4937
Windows (Command Prompt)
netstat -ano | findstr :4937
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 4937

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4937

Block port 4937 in the firewall

ufw
sudo ufw deny 4937/udp
iptables
sudo iptables -A INPUT -p udp --dport 4937 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4937 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4937' -Direction Inbound -Protocol UDP -LocalPort 4937 -Action Block

Related ports

4930fmsg4936an-signaling4940eq-office-49404941eq-office-4941

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.