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Port 1648 (concurrent-lm)

IANA assigns port 1648 to concurrent-lm.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
concurrent-lm TCP concurrent-lm Maggie Brinsford -
concurrent-lm UDP concurrent-lm Maggie Brinsford -

Check what is listening on port 1648

Linux: is anything listening on TCP 1648?
sudo ss -tlnp 'sport = :1648'
Linux: UDP 1648
sudo ss -ulnp 'sport = :1648'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1648
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1648 '
Windows (Command Prompt)
netstat -ano | findstr :1648
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1648 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1648
From Windows
Test-NetConnection HOST -Port 1648
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1648

Block port 1648 in the firewall

ufw
sudo ufw deny 1648/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1648 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1648 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1648' -Direction Inbound -Protocol TCP -LocalPort 1648 -Action Block
ufw
sudo ufw deny 1648/udp
iptables
sudo iptables -A INPUT -p udp --dport 1648 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1648 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1648' -Direction Inbound -Protocol UDP -LocalPort 1648 -Action Block

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