Port 6503 (boks-clntd, boks_clntd)

IANA assigns port 6503 to boks-clntd, boks_clntd: BoKS Clntd IANA assigned this well-formed service name as a replacement for "boks_clntd"..

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

boks-clntd TCP BoKS Clntd IANA assigned this well-formed service name as a replacement for "boks_clntd". Magnus Nystrom -

boks_clntd TCP BoKS Clntd
This entry is an alias to "boks-clntd". This entry is now historic, not usable for use with many common service discovery mechanisms. Magnus Nystrom -

boks-clntd UDP BoKS Clntd IANA assigned this well-formed service name as a replacement for "boks_clntd". Magnus Nystrom -

boks_clntd UDP BoKS Clntd
This entry is an alias to "boks-clntd". This entry is now historic, not usable for use with many common service discovery mechanisms. Magnus Nystrom -

Check what is listening on port 6503

Linux: is anything listening on TCP 6503?

sudo ss -tlnp 'sport = :6503'

Linux: UDP 6503

sudo ss -ulnp 'sport = :6503'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6503

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':6503 '

Windows (Command Prompt)

netstat -ano | findstr :6503

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6503 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 6503

From Windows

Test-NetConnection HOST -Port 6503

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

nc -vzu -w 5 HOST 6503

Block port 6503 in the firewall

ufw

sudo ufw deny 6503/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 6503 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 6503 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 6503' -Direction Inbound -Protocol TCP -LocalPort 6503 -Action Block

ufw

sudo ufw deny 6503/udp