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Port 3501 (isoft-p2p)

IANA assigns port 3501 to isoft-p2p: iSoft-P2P.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
isoft-p2p TCP iSoft-P2P David Walling 2 -
isoft-p2p UDP iSoft-P2P David Walling 2 -

Check what is listening on port 3501

Linux: is anything listening on TCP 3501?
sudo ss -tlnp 'sport = :3501'
Linux: UDP 3501
sudo ss -ulnp 'sport = :3501'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3501
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3501 '
Windows (Command Prompt)
netstat -ano | findstr :3501
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3501 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3501
From Windows
Test-NetConnection HOST -Port 3501
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3501

Block port 3501 in the firewall

ufw
sudo ufw deny 3501/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3501 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3501 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3501' -Direction Inbound -Protocol TCP -LocalPort 3501 -Action Block
ufw
sudo ufw deny 3501/udp
iptables
sudo iptables -A INPUT -p udp --dport 3501 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3501 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3501' -Direction Inbound -Protocol UDP -LocalPort 3501 -Action Block

Related ports

3499sccip-media3500rtmp-port3502avinstalldisc3503lsp-ping

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