Port 27015 — Source Engine (UDP)
What is Port 27015?
Digunakan oleh permainan Valve (CS:GO, TF2, Half‑Life) untuk pelayan khusus.
This is a registered port (1024–49151) often assigned to vendor or application services like Source Engine. · No formal RFC; Valve Source Engine protocol
When do you need Port 27015 open?
Open if you are hosting a Source engine game server (CS2, TF2, Garry's Mod) for external players. Requires a port forwarding rule on your router pointing to the server's local IP address.
Common uses and software
- Counter-Strike 2 (CS2)
- Team Fortress 2 (TF2)
- Left 4 Dead 2
- Garry's Mod
- Valve Dedicated Server (SrcDS)
Security
Source servers can be targeted by UDP reflection and amplification attacks. Keep the SrcDS binary updated via SteamCMD — Valve issues security patches regularly. Enable Valve Anti-Cheat (VAC). Set a strong RCON password and consider using an IP allowlist for RCON access. Rate-limit incoming traffic at the router if you experience DDoS.
Is Port 27015 safe?
An open port increases your attack surface. Safety depends on how Source Engine is configured.
Low risk, but confirm that Source Engine on this port is intentionally running and required by your application before leaving it open.
Test connectivity for Port 27015 on any host.
How to Open Port 27015
To allow incoming connections to Port 27015 (Source Engine) from outside your network, configure your firewall and add a port forwarding rule on your router pointing to your device's local IP address.
Open Windows Defender Firewall → Advanced Settings → Inbound Rules → New Rule → Port → UDP → Specific local ports: 27015 → Allow the connection → Name and save the rule.
netsh advfirewall firewall add rule name="Open Port 27015" dir=in action=allow protocol=udp localport=27015sudo ufw allow 27015/udpsudo iptables -A INPUT -p udp --dport 27015 -j ACCEPTLog into your router (192.168.1.1 or 192.168.0.1) → Port Forwarding → Add a new rule: Protocol UDP, External port 27015, Internal IP: your device's local IP, Internal port 27015 → Save.
How to close Port 27015
If you do not need Source Engine, block this port in your firewall or router.
To block port 27015 on Windows, run the following command in PowerShell or Command Prompt (as Administrator):
netsh advfirewall firewall add rule name="Block Port 27015" dir=in action=block protocol=udp localport=27015sudo ufw deny 27015/udpsudo iptables -A INPUT -p udp --dport 27015 -j DROPRemove or disable any port forwarding rule for Port 27015.
Frequently Asked Questions
What is Port 27015 used for?▾
Port 27015 is the default UDP port for Source Engine. It is used by servers and applications that need to accept incoming connections for this service. Whether you need it open depends on whether you are actively running a Source Engine server — if not, it should remain closed to reduce your attack surface.
Is Port 27015 safe to keep open?▾
An open Port 27015 increases your attack surface. If you are not actively running Source Engine, close this port in your firewall and remove any port forwarding rules. If Source Engine must be accessible, restrict access to known IP ranges, keep the service software updated with security patches, and use strong authentication.