Port 3690 Subversion · TCP

What runs on port 3690

Subversion's svnserve protocol (svn://). Plaintext with its own simple authentication; svn+ssh and HTTPS (mod_dav_svn) are the encrypted ways to serve Subversion, and what most remaining installations use.

Software that uses it: svnserve · VisualSVN · TortoiseSVN (client)

Should port 3690 be open?

Private network or VPN only. Nothing good comes from this port being reachable from the internet. Keep it on an internal network, reach it over a VPN or an SSH tunnel, and firewall it from everything that does not need it.

• Prefer https:// or svn+ssh:// URLs; keep 3690 for a trusted LAN only.

Check port 3690

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :3690'
sudo lsof -i :3690

# from another machine: is it reachable?
nc -zv host 3690
nmap -p 3690 host
curl -v telnet://host:3690      # 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 3690

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 3690 proto tcp
sudo ufw deny 3690/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 3690 accept
nft add rule inet filter input tcp dport 3690 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 3690 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 3690 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=3690 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 3690" with no source is just "open".

Putting it behind nginx

server {
    listen 443 ssl;
    server_name app.example.com;
    location / {
        proxy_pass http://127.0.0.1:3690;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto https;
    }
}

Then make the application listen on 127.0.0.1:3690 only. Test which location block a request hits with the nginx location tester.

Related ports

• 9418 git — git:// protocol
• 22 SSH — SSH, SCP, SFTP, git over ssh
• 443 HTTPS — Web over TLS; UDP for HTTP/3 (QUIC)

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