NetBIOS over TCP / IP
NetBIOS over TCP / IP (short NetBT or NBT ) is a network protocol which enables programs based on the NetBIOS programming interface to be used via the network protocol TCP / IP .
NBT is defined in the RFC documents RFC 1001 (overview) and RFC 1002 (details).
The NetBIOS name resolution is handled over UDP on port 137, the datagram service over UDP on port 138 and the session service over TCP on port 139. The UDP packets or TCP connections each have headers at the beginning with information such as the NetBIOS name of the sender and recipient.
Windows versions up to Windows ME used NBT to implement the higher network functions ( Server Message Block (SMB)). Windows versions from Windows 2000 onwards handle SMB communication directly via TCP port 445.