Port 9735 Lightning Network · TCP

What runs on port 9735

Lightning Network peer-to-peer port (LND, Core Lightning, Eclair). A routing node needs it reachable for inbound channels; the RPC/REST APIs (10009, 8080 in LND) must not be.

Software that uses it: LND · Core Lightning · Eclair

Should port 9735 be open?

Designed to face the internet. This port exists to be reachable from anywhere, so the usual question is not whether to open it but how the service behind it is configured and patched.

• Tor hidden services are common for Lightning nodes to avoid exposing a home IP.

Check port 9735

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :9735'
sudo lsof -i :9735

# from another machine: is it reachable?
nc -zv host 9735
nmap -p 9735 host
curl -v telnet://host:9735      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 9735

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 9735 proto tcp
sudo ufw deny 9735/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 9735 accept
nft add rule inet filter input tcp dport 9735 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 9735 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9735 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=9735 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 9735" with no source is just "open".

Related ports

• 8333 Bitcoin

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions