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Port 3357 (adtech-test)

IANA assigns port 3357 to adtech-test: Adtech Test IP.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
adtech-test TCP Adtech Test IP Robin Uyeshiro -
adtech-test UDP Adtech Test IP Robin Uyeshiro -

Check what is listening on port 3357

Linux: is anything listening on TCP 3357?
sudo ss -tlnp 'sport = :3357'
Linux: UDP 3357
sudo ss -ulnp 'sport = :3357'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3357
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3357 '
Windows (Command Prompt)
netstat -ano | findstr :3357
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3357 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3357
From Windows
Test-NetConnection HOST -Port 3357
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3357

Block port 3357 in the firewall

ufw
sudo ufw deny 3357/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3357 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3357 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3357' -Direction Inbound -Protocol TCP -LocalPort 3357 -Action Block
ufw
sudo ufw deny 3357/udp
iptables
sudo iptables -A INPUT -p udp --dport 3357 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3357 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3357' -Direction Inbound -Protocol UDP -LocalPort 3357 -Action Block

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