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Port 4073 (iRAPP)

IANA assigns port 4073 to iRAPP: Interactive Remote Application Pairing Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
iRAPP TCP Interactive Remote Application Pairing Protocol Volodymyr Bykov -
iRAPP UDP Interactive Remote Application Pairing Protocol Volodymyr Bykov -

Registry dates for this port: registered 2007-08-20, last modified 2016-11-23.

Check what is listening on port 4073

Linux: is anything listening on TCP 4073?
sudo ss -tlnp 'sport = :4073'
Linux: UDP 4073
sudo ss -ulnp 'sport = :4073'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4073
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4073 '
Windows (Command Prompt)
netstat -ano | findstr :4073
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4073 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4073
From Windows
Test-NetConnection HOST -Port 4073
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4073

Block port 4073 in the firewall

ufw
sudo ufw deny 4073/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4073 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4073 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4073' -Direction Inbound -Protocol TCP -LocalPort 4073 -Action Block
ufw
sudo ufw deny 4073/udp
iptables
sudo iptables -A INPUT -p udp --dport 4073 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4073 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4073' -Direction Inbound -Protocol UDP -LocalPort 4073 -Action Block

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