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Port 158 (pcmail-srv)

IANA assigns port 158 to pcmail-srv: PCMail Server.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
pcmail-srv TCP PCMail Server Mark L Lambert -
pcmail-srv UDP PCMail Server Mark L Lambert -

Check what is listening on port 158

Linux: is anything listening on TCP 158?
sudo ss -tlnp 'sport = :158'
Linux: UDP 158
sudo ss -ulnp 'sport = :158'
Linux / macOS: which process owns the port
sudo lsof -nP -i :158
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':158 '
Windows (Command Prompt)
netstat -ano | findstr :158
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 158 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 158
From Windows
Test-NetConnection HOST -Port 158
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 158

Block port 158 in the firewall

ufw
sudo ufw deny 158/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 158 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 158 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 158' -Direction Inbound -Protocol TCP -LocalPort 158 -Action Block
ufw
sudo ufw deny 158/udp
iptables
sudo iptables -A INPUT -p udp --dport 158 -j DROP
nftables
sudo nft add rule inet filter input udp dport 158 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 158' -Direction Inbound -Protocol UDP -LocalPort 158 -Action Block

Related ports

156sqlsrv157knet-cmp159nss-routing160sgmp-traps

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