Port 139
netbios-ssn · TCP/UDP
| Range | System/well-known port (0–1023) |
|---|---|
| Protocol | TCP/UDP |
| Service | netbios-ssn |
Frequently asked questions
What is port 139 used for?
Port 139 is registered with the IANA for netbios-ssn (TCP/UDP). Description: NETBIOS Session Service.
Is port 139 a well-known port?
Yes. Port 139 is in the range 0–1023 (system or well-known ports). On Linux and macOS only privileged processes may bind to these ports.
How do I check whether port 139 is open?
Locally on Linux with ss -tulpn | grep ':139\b', on Windows with netstat -ano | findstr :139. To test a remote host use Test-NetConnection <host> -Port 139 in PowerShell or nc -zv <host> 139 on Linux/macOS.
How do I open port 139 in the firewall?
Ubuntu/Debian (ufw): sudo ufw allow 139/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=139/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 139" -Direction Inbound -Protocol TCP -LocalPort 139 -Action Allow.
IANA registry entries
| Protocol | Service | Description (IANA) |
|---|---|---|
| TCP | netbios-ssn | NETBIOS Session Service |
| UDP | netbios-ssn | NETBIOS Session Service |