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Port 246 (dsp3270)

IANA assigns port 246 to dsp3270: Display Systems Protocol.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dsp3270 TCP Display Systems Protocol Weldon J Showalter -
dsp3270 UDP Display Systems Protocol Weldon J Showalter -

Check what is listening on port 246

Linux: is anything listening on TCP 246?
sudo ss -tlnp 'sport = :246'
Linux: UDP 246
sudo ss -ulnp 'sport = :246'
Linux / macOS: which process owns the port
sudo lsof -nP -i :246
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':246 '
Windows (Command Prompt)
netstat -ano | findstr :246
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 246 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 246
From Windows
Test-NetConnection HOST -Port 246
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 246

Block port 246 in the firewall

ufw
sudo ufw deny 246/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 246 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 246 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 246' -Direction Inbound -Protocol TCP -LocalPort 246 -Action Block
ufw
sudo ufw deny 246/udp
iptables
sudo iptables -A INPUT -p udp --dport 246 -j DROP
nftables
sudo nft add rule inet filter input udp dport 246 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 246' -Direction Inbound -Protocol UDP -LocalPort 246 -Action Block

Related ports

244inbusiness245link247subntbcst-tftp, subntbcst_tftp248bhfhs

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