HTTPfy

Port 593 (RPC over HTTP)

Microsoft RPC endpoint mapper over HTTP, used by Outlook Anywhere and some AD tooling.

Well-known (system) port, 0-1023 TCP Windows networking Do not expose to the internet

What port 593 is used for

Microsoft RPC endpoint mapper over HTTP, used by Outlook Anywhere and some AD tooling.

Security: should port 593 be open?

Do not expose to the internet. Block at the perimeter like 135.

IANA assignment

Service nameProtoDescriptionAssigneeReference
http-rpc-epmap TCP HTTP RPC Ep Map Edward Reus -
http-rpc-epmap UDP HTTP RPC Ep Map Edward Reus -

Check what is listening on port 593

Linux: is anything listening on TCP 593?
sudo ss -tlnp 'sport = :593'
Linux / macOS: which process owns the port
sudo lsof -nP -i :593
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':593 '
Windows (Command Prompt)
netstat -ano | findstr :593
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 593 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 593
From Windows
Test-NetConnection HOST -Port 593

Block port 593 in the firewall

ufw
sudo ufw deny 593/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 593 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 593 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 593' -Direction Inbound -Protocol TCP -LocalPort 593 -Action Block

Related ports

135Microsoft RPC endpoint mapper445SMB (Microsoft-DS)591http-alt592eudora-set594tpip595cab-protocol

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.