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Port 4901 (flr-agent, flr_agent)

IANA assigns port 4901 to flr-agent, flr_agent: FileLocator Remote Search Agent IANA assigned this well-formed service name as a replacement for "flr_agent"..

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
flr-agent TCP FileLocator Remote Search Agent IANA assigned this well-formed service name as a replacement for "flr_agent". David Vest -
flr_agent TCP FileLocator Remote Search Agent
This entry is an alias to "flr-agent". This entry is now historic, not usable for use with many common service discovery mechanisms. David Vest -

Registry dates for this port: registered 2008-11-19.

Check what is listening on port 4901

Linux: is anything listening on TCP 4901?
sudo ss -tlnp 'sport = :4901'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4901
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4901 '
Windows (Command Prompt)
netstat -ano | findstr :4901
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4901 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4901
From Windows
Test-NetConnection HOST -Port 4901

Block port 4901 in the firewall

ufw
sudo ufw deny 4901/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4901 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4901' -Direction Inbound -Protocol TCP -LocalPort 4901 -Action Block

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