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Port 4842 (gw-asv)

IANA assigns port 4842 to gw-asv: nCode ICE-flow Library AppServer.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
gw-asv TCP nCode ICE-flow Library AppServer Ross Swithenbank -
gw-asv UDP nCode ICE-flow Library AppServer Ross Swithenbank -

Registry dates for this port: registered 2006-09, last modified 2017-05-23.

Check what is listening on port 4842

Linux: is anything listening on TCP 4842?
sudo ss -tlnp 'sport = :4842'
Linux: UDP 4842
sudo ss -ulnp 'sport = :4842'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4842
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4842 '
Windows (Command Prompt)
netstat -ano | findstr :4842
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4842 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4842
From Windows
Test-NetConnection HOST -Port 4842
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4842

Block port 4842 in the firewall

ufw
sudo ufw deny 4842/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4842 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4842 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4842' -Direction Inbound -Protocol TCP -LocalPort 4842 -Action Block
ufw
sudo ufw deny 4842/udp
iptables
sudo iptables -A INPUT -p udp --dport 4842 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4842 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4842' -Direction Inbound -Protocol UDP -LocalPort 4842 -Action Block

Related ports

4840opcua-tcp, opcua-udp4841quosa4843opcua-tls4844gw-log

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