HTTPfy

Port 4556 (dtn-bundle)

IANA assigns port 4556 to dtn-bundle: DTN Bundle TCP CL Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dtn-bundle TCP DTN Bundle TCP CL Protocol IESG RFC 9174
dtn-bundle UDP DTN Bundle UDP CL Protocol - RFC 7122
dtn-bundle DCCP DTN Bundle DCCP CL Protocol - RFC 7122

Registry dates for this port: registered 2006-11, last modified 2021-02-22.

Check what is listening on port 4556

Linux: is anything listening on TCP 4556?
sudo ss -tlnp 'sport = :4556'
Linux: UDP 4556
sudo ss -ulnp 'sport = :4556'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4556
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4556 '
Windows (Command Prompt)
netstat -ano | findstr :4556
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4556 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4556
From Windows
Test-NetConnection HOST -Port 4556
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4556

Block port 4556 in the firewall

ufw
sudo ufw deny 4556/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4556 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4556 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4556' -Direction Inbound -Protocol TCP -LocalPort 4556 -Action Block
ufw
sudo ufw deny 4556/udp
iptables
sudo iptables -A INPUT -p udp --dport 4556 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4556 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4556' -Direction Inbound -Protocol UDP -LocalPort 4556 -Action Block

Related ports

4554msfrs4555rsip4557mtcevrunqss4558mtcevrunqman

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