HTTPfy

Port 1973 (dlsrap)

IANA assigns port 1973 to dlsrap: Data Link Switching Remote Access Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dlsrap TCP Data Link Switching Remote Access Protocol Steve T Chiang -
dlsrap UDP Data Link Switching Remote Access Protocol Steve T Chiang -

Check what is listening on port 1973

Linux: is anything listening on TCP 1973?
sudo ss -tlnp 'sport = :1973'
Linux: UDP 1973
sudo ss -ulnp 'sport = :1973'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1973
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1973 '
Windows (Command Prompt)
netstat -ano | findstr :1973
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1973 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1973
From Windows
Test-NetConnection HOST -Port 1973
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1973

Block port 1973 in the firewall

ufw
sudo ufw deny 1973/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1973 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1973 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1973' -Direction Inbound -Protocol TCP -LocalPort 1973 -Action Block
ufw
sudo ufw deny 1973/udp
iptables
sudo iptables -A INPUT -p udp --dport 1973 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1973 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1973' -Direction Inbound -Protocol UDP -LocalPort 1973 -Action Block

Related ports

1971netop-school1972intersys-cache1974drp1975tcoflashagent

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