Port 7543 (atul)

IANA assigns port 7543 to atul: atul server.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

atul TCP atul server Mark Stapp -

atul UDP atul server Mark Stapp -

Registry dates for this port: registered 2006-01.

Linux: is anything listening on TCP 7543?

sudo ss -tlnp 'sport = :7543'

Linux: UDP 7543

sudo ss -ulnp 'sport = :7543'

Linux / macOS: which process owns the port

sudo lsof -nP -i :7543

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':7543 '

Windows (Command Prompt)

netstat -ano | findstr :7543

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 7543 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 7543

From Windows

Test-NetConnection HOST -Port 7543

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 7543

ufw

sudo ufw deny 7543/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 7543 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 7543 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 7543' -Direction Inbound -Protocol TCP -LocalPort 7543 -Action Block

ufw

sudo ufw deny 7543/udp

iptables

sudo iptables -A INPUT -p udp --dport 7543 -j DROP

nftables

sudo nft add rule inet filter input udp dport 7543 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 7543' -Direction Inbound -Protocol UDP -LocalPort 7543 -Action Block

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