Port 21213 (cohesity-agent)

IANA assigns port 21213 to cohesity-agent: Cohesity backup agents.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

cohesity-agent TCP Cohesity backup agents Cohesity Inc -

Registry dates for this port: registered 2019-08-01.

Linux: is anything listening on TCP 21213?

sudo ss -tlnp 'sport = :21213'

Linux / macOS: which process owns the port

sudo lsof -nP -i :21213

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':21213 '

Windows (Command Prompt)

netstat -ano | findstr :21213

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 21213 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 21213

From Windows

Test-NetConnection HOST -Port 21213

ufw

sudo ufw deny 21213/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 21213 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 21213 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 21213' -Direction Inbound -Protocol TCP -LocalPort 21213 -Action Block

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