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Port 1336 (ischat)

IANA assigns port 1336 to ischat: Instant Service Chat.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
ischat TCP Instant Service Chat Mike Clise -
ischat UDP Instant Service Chat Mike Clise -

Check what is listening on port 1336

Linux: is anything listening on TCP 1336?
sudo ss -tlnp 'sport = :1336'
Linux: UDP 1336
sudo ss -ulnp 'sport = :1336'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1336
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1336 '
Windows (Command Prompt)
netstat -ano | findstr :1336
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1336 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1336
From Windows
Test-NetConnection HOST -Port 1336
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1336

Block port 1336 in the firewall

ufw
sudo ufw deny 1336/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1336 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1336 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1336' -Direction Inbound -Protocol TCP -LocalPort 1336 -Action Block
ufw
sudo ufw deny 1336/udp
iptables
sudo iptables -A INPUT -p udp --dport 1336 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1336 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1336' -Direction Inbound -Protocol UDP -LocalPort 1336 -Action Block

Related ports

1334writesrv1335digital-notary1337menandmice-dns1338wmc-log-svc

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