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Port 1901 (fjicl-tep-a)

IANA assigns port 1901 to fjicl-tep-a: Fujitsu ICL Terminal Emulator Program A.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
fjicl-tep-a TCP Fujitsu ICL Terminal Emulator Program A Bob Lyon -
fjicl-tep-a UDP Fujitsu ICL Terminal Emulator Program A Bob Lyon -

Check what is listening on port 1901

Linux: is anything listening on TCP 1901?
sudo ss -tlnp 'sport = :1901'
Linux: UDP 1901
sudo ss -ulnp 'sport = :1901'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1901
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1901 '
Windows (Command Prompt)
netstat -ano | findstr :1901
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1901 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1901
From Windows
Test-NetConnection HOST -Port 1901
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1901

Block port 1901 in the firewall

ufw
sudo ufw deny 1901/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1901 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1901' -Direction Inbound -Protocol TCP -LocalPort 1901 -Action Block
ufw
sudo ufw deny 1901/udp
iptables
sudo iptables -A INPUT -p udp --dport 1901 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1901' -Direction Inbound -Protocol UDP -LocalPort 1901 -Action Block

Related ports

1899mc2studios1900SSDP / UPnP1902fjicl-tep-b1903linkname

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