HTTPfy

Port 3751 (gprs-cube)

IANA assigns port 3751 to gprs-cube: CommLinx GPRS Cube.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
gprs-cube TCP CommLinx GPRS Cube Peter Johnson -
gprs-cube UDP CommLinx GPRS Cube Peter Johnson -

Registry dates for this port: registered 2003-04.

Check what is listening on port 3751

Linux: is anything listening on TCP 3751?
sudo ss -tlnp 'sport = :3751'
Linux: UDP 3751
sudo ss -ulnp 'sport = :3751'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3751
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3751 '
Windows (Command Prompt)
netstat -ano | findstr :3751
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3751 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3751
From Windows
Test-NetConnection HOST -Port 3751
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3751

Block port 3751 in the firewall

ufw
sudo ufw deny 3751/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3751 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3751 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3751' -Direction Inbound -Protocol TCP -LocalPort 3751 -Action Block
ufw
sudo ufw deny 3751/udp
iptables
sudo iptables -A INPUT -p udp --dport 3751 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3751 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3751' -Direction Inbound -Protocol UDP -LocalPort 3751 -Action Block

Related ports

3749cimtrak3750cbos-ip-port3752vipremoteagent3753nattyserver

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