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Port 5581 (tmosms1)

IANA assigns port 5581 to tmosms1: T-Mobile SMS Protocol Message 1.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
tmosms1 TCP T-Mobile SMS Protocol Message 1 Ezinne Oji -
tmosms1 UDP T-Mobile SMS Protocol Message 1 Ezinne Oji -

Registry dates for this port: registered 2006-06.

Check what is listening on port 5581

Linux: is anything listening on TCP 5581?
sudo ss -tlnp 'sport = :5581'
Linux: UDP 5581
sudo ss -ulnp 'sport = :5581'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5581
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5581 '
Windows (Command Prompt)
netstat -ano | findstr :5581
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5581 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5581
From Windows
Test-NetConnection HOST -Port 5581
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5581

Block port 5581 in the firewall

ufw
sudo ufw deny 5581/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5581 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5581 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5581' -Direction Inbound -Protocol TCP -LocalPort 5581 -Action Block
ufw
sudo ufw deny 5581/udp
iptables
sudo iptables -A INPUT -p udp --dport 5581 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5581 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5581' -Direction Inbound -Protocol UDP -LocalPort 5581 -Action Block

Related ports

5579fdtracks5580tmosms05582fac-restore5583tmo-icon-sync

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