Port 139 — NetBIOS
NetBIOS Session Service — legacy Windows file and printer sharing.
| Port number | 139 |
|---|---|
| Service | NetBIOS |
| Transport | TCP |
| Category | File Transfer |
Is port 139 safe?
Should never be internet-facing; a classic attack surface.
Frequently asked questions
What is port 139 used for?
Port 139 (TCP) is the standard port for NetBIOS. NetBIOS Session Service — legacy Windows file and printer sharing.
Is port 139 safe to open?
Should never be internet-facing; a classic attack surface.
Is port 139 TCP or UDP?
Port 139 commonly uses TCP.