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Port 1981 (p2pq)

IANA assigns port 1981 to p2pq: p2pQ.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
p2pq TCP p2pQ Warren Alexander -
p2pq UDP p2pQ Warren Alexander -

Check what is listening on port 1981

Linux: is anything listening on TCP 1981?
sudo ss -tlnp 'sport = :1981'
Linux: UDP 1981
sudo ss -ulnp 'sport = :1981'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1981
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1981 '
Windows (Command Prompt)
netstat -ano | findstr :1981
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1981 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1981
From Windows
Test-NetConnection HOST -Port 1981
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1981

Block port 1981 in the firewall

ufw
sudo ufw deny 1981/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1981 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1981 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1981' -Direction Inbound -Protocol TCP -LocalPort 1981 -Action Block
ufw
sudo ufw deny 1981/udp
iptables
sudo iptables -A INPUT -p udp --dport 1981 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1981 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1981' -Direction Inbound -Protocol UDP -LocalPort 1981 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.