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Port 9091 (Prometheus Pushgateway / Transmission)

Prometheus Pushgateway, and the Transmission BitTorrent client's web UI.

Registered (user) port, 1024-49151 TCP Monitoring and logging Do not expose to the internet

What port 9091 is used for

Prometheus Pushgateway, and the Transmission BitTorrent client's web UI.

Security: should port 9091 be open?

Do not expose to the internet. Both lack strong auth by default; keep them internal.

IANA assignment

Service nameProtoDescriptionAssigneeReference
xmltec-xmlmail TCP xmltec-xmlmail Mitch Kaufman -
xmltec-xmlmail UDP xmltec-xmlmail Mitch Kaufman -

Check what is listening on port 9091

Linux: is anything listening on TCP 9091?
sudo ss -tlnp 'sport = :9091'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9091
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':9091 '
Windows (Command Prompt)
netstat -ano | findstr :9091
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9091 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 9091
From Windows
Test-NetConnection HOST -Port 9091

Block port 9091 in the firewall

ufw
sudo ufw deny 9091/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 9091 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 9091 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 9091' -Direction Inbound -Protocol TCP -LocalPort 9091 -Action Block

Related ports

9090Prometheus9093Prometheus Alertmanager9089sqlexec-ssl9092Apache Kafka

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