Microsoft Message Queuing — a Windows server moving application messages between queues.
MSMQ uses TCP 1801 to establish the session over which messages are sent between Message Queuing computers, and Microsoft's firewall guidance treats it as the bare minimum port to open, alongside RPC on 135 and 2101/2103/2105 for remote queue access and a UDP 3527 ping. It is a Windows Server feature, so a listener here means a .NET or BizTalk application tier doing asynchronous work — order processing, integration middleware, line-of-business back ends. Microsoft registered 1801 with IANA for exactly this.
Do not expose
CVE-2023-21554 ("QueueJumper") was an unauthenticated remote code execution reachable by a single packet to 1801, and MSMQ has drawn repeated critical advisories since — this is an internal application transport and must never face the internet.
$ nc -vz -w 3 TARGET 1801Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
Get Beige Box →also available as JSON · Markdown
Corrections or a missing port? Reply @rimrocksystems.