NetBIOS and Samba Ports

Service Name Port Protocol
Name Resolution Service 137 UDP
Datagram Services (browsing) 138 UDP
Session Service 139 TCP
SMB 445 TCP Input, UDP Output

Observations

These are the contents of /etc/services:

netbios-ns 137/udp   # NetBIOS Name Service  
netbios-dgm 138/udp  # NetBIOS Datagram Service  
netbios-ssn 139/tcp  # NetBIOS Session Service  
microsoft-ds 445/tcp # Microsoft Directory Service

These are the ports that the Samba server listens on. A few things here:

  1. The first three are ports ports used by Windows to ‚Äėfind‚Äô other
    computers (a la ‚ÄúMy Network‚ÄĚ)
  2. The last is for directory services
  3. UDP 137 and 138 are serviced by nmbd
  4. TCP 139 and 445 are serviced by smbd

Sources