HTTPfy

Port 57 (any private terminal access)

IANA assigns port 57 to any private terminal access.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
- TCP any private terminal access Jon Postel -
- UDP any private terminal access Jon Postel -

Check what is listening on port 57

Linux: is anything listening on TCP 57?
sudo ss -tlnp 'sport = :57'
Linux: UDP 57
sudo ss -ulnp 'sport = :57'
Linux / macOS: which process owns the port
sudo lsof -nP -i :57
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':57 '
Windows (Command Prompt)
netstat -ano | findstr :57
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 57 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 57
From Windows
Test-NetConnection HOST -Port 57
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 57

Block port 57 in the firewall

ufw
sudo ufw deny 57/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 57 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 57 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 57' -Direction Inbound -Protocol TCP -LocalPort 57 -Action Block
ufw
sudo ufw deny 57/udp
iptables
sudo iptables -A INPUT -p udp --dport 57 -j DROP
nftables
sudo nft add rule inet filter input udp dport 57 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 57' -Direction Inbound -Protocol UDP -LocalPort 57 -Action Block

Related ports

55isi-gl56xns-auth58xns-mail59any private file service

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