Port 9877 (x510)

IANA assigns port 9877 to x510: The X.510 wrapper protocol.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

x510 TCP The X.510 wrapper protocol ITU TSB ITU-T Study Group 17 ITU-T X.510 / ISO/IEC 9584-11

Registry dates for this port: registered 2019-09-30.

Linux: is anything listening on TCP 9877?

sudo ss -tlnp 'sport = :9877'

Linux / macOS: which process owns the port

sudo lsof -nP -i :9877

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':9877 '

Windows (Command Prompt)

netstat -ano | findstr :9877

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9877 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 9877

From Windows

Test-NetConnection HOST -Port 9877

ufw

sudo ufw deny 9877/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 9877 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 9877 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 9877' -Direction Inbound -Protocol TCP -LocalPort 9877 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.