| Service | Port | Protocol | Purpose | |---------|------|----------|---------| | Name Service | 137 | UDP/TCP | Register/resolve NetBIOS names | | Datagram Service | | UDP | Connectionless broadcast/multicast messages | | Session Service | 139 | TCP | Connection-oriented file/print sharing |
When paired with —the Linux, Unix, and BSD daemon that implements the Server Message Block (SMB) protocol—port 170 plays a critical role in NetBIOS datagram distribution. While modern Windows environments have shifted toward Direct SMB over TCP (port 445), countless industrial systems, older file servers, and hybrid networks still rely on the SMBd service’s ability to manage NetBIOS over TCP/IP. This article explores the technical depths of SMBd, the precise function of port 170, and why understanding this combination remains essential for system administrators today. Part 1: What is SMBd? The Heart of Samba 1.1 The Samba Suite SMBd is the core component of the Samba project, an open-source reimplementation of Microsoft’s SMB protocol suite. First released in 1992 by Andrew Tridgell, Samba allowed Unix-like systems to act as full-fledged Windows file and print servers.
sudo systemctl restart nmbd sudo systemctl restart smbd After this change, nmbd will send and receive datagram packets on UDP 170 instead of UDP 138. Clients must be configured to match, making this a purely internal or testing configuration. A tcpdump capture on a Samba server using port 170 would show: smbd 170
sudo tcpdump -i eth0 udp port 170 Sample output:
[global] datagram port = 170 dgram port = 170 # older syntax Then restart Samba: | Service | Port | Protocol | Purpose
The SMBd daemon, through its unassuming configuration options, embodies the philosophy of Samba: . Whether on standard UDP 138 or on an obscure port like 170, the daemon faithfully translates between the messy reality of legacy Windows networking and the clean world of POSIX systems.
[global] disable netbios = yes smb ports = 445 Despite Microsoft’s deprecation of SMB1 and NetBIOS, countless embedded devices, medical imaging systems, and CNC machines still speak only NetBIOS over UDP ports 137/138 (or custom variants like port 170). For those administrators, SMBd remains a lifeline. Part 6: Troubleshooting Port 170 in SMBd 6.1 Verifying That SMBd/NMBd Is Listening Use netstat or ss : Part 1: What is SMBd
sudo ss -ulnp | grep :170 Expected output: