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Port 3251 (sysscanner)

IANA assigns port 3251 to sysscanner: Sys Scanner.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sysscanner TCP Sys Scanner Dick Georges -
sysscanner UDP Sys Scanner Dick Georges -

Registry dates for this port: registered 2002-02.

Check what is listening on port 3251

Linux: is anything listening on TCP 3251?
sudo ss -tlnp 'sport = :3251'
Linux: UDP 3251
sudo ss -ulnp 'sport = :3251'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3251
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3251 '
Windows (Command Prompt)
netstat -ano | findstr :3251
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3251 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3251
From Windows
Test-NetConnection HOST -Port 3251
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3251

Block port 3251 in the firewall

ufw
sudo ufw deny 3251/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3251 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3251 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3251' -Direction Inbound -Protocol TCP -LocalPort 3251 -Action Block
ufw
sudo ufw deny 3251/udp
iptables
sudo iptables -A INPUT -p udp --dport 3251 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3251 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3251' -Direction Inbound -Protocol UDP -LocalPort 3251 -Action Block

Related ports

3249ssp3250hicp3252dhe3253pda-data

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