Well-known · Windows

138 NetBIOS Datagram

TCP Assigned
UDP Yes
SCTP —
DCCP —

What it is

NetBIOS datagram (connectionless) service.

When / why

Legacy Windows browsing/announcements.

Protocol status detail

TransportStatusMeaning
TCP Assigned Assigned by IANA, but not standardized, specified, or widely used on this port.
UDP Yes Assigned by IANA and standardized, specified, or widely used on this port.
SCTP — Not applicable for this transport.
DCCP — Not applicable for this transport.
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Port range

Well-known (0–1023). System port for a core service. On Unix-like systems, binding it requires superuser privileges.

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