# WHATPORT(593)

## NAME

port 593 — HTTP RPC endpoint mapper (RPC over HTTP) — Windows RPC tunnelled over HTTP — the endpoint mapper for RPC/HTTP, historically Outlook Anywhere.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA registers TCP 593 as "http-rpc-epmap": the HTTP RPC endpoint mapper. Microsoft's RPC over HTTP protocol ([MS-RPCH]) tunnels DCE/RPC traffic through an RPC-over-HTTP proxy so it can traverse firewalls, and 593 is the endpoint-mapper counterpart to the plain DCE endpoint mapper on TCP 135. Its best-known consumer was Outlook Anywhere against Exchange; the proxy itself normally publishes over 443, so 593 turning up on a scan is a Windows server exposing the RPC/HTTP plumbing directly.

## EXPOSURE

**Do not expose.** This is an RPC control plane. Every reason TCP 135 is blocked at the perimeter applies here — clients should reach RPC/HTTP through the HTTPS proxy on 443, never this port.

## CHECK

```sh
nc -vz -w 3 TARGET 593
```

## SEE ALSO

- docs — [[MS-RPCH]: Remote Procedure Call over HTTP Protocol](https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-rpch/c0f4c9c5-1a61-4d10-b8e2-005378d1d212) (learn.microsoft.com)
- iana — [IANA Service Name and Transport Protocol Port Number Registry — 593](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=593) (iana.org)

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HTML: <https://whatport.net/593/> · JSON: <https://whatport.net/593.json> · full dataset: <https://whatport.net/ports.json>