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Port 3203 (netwatcher-mon)

IANA assigns port 3203 to netwatcher-mon: Network Watcher Monitor.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
netwatcher-mon TCP Network Watcher Monitor - -
netwatcher-mon UDP Network Watcher Monitor - -

Check what is listening on port 3203

Linux: is anything listening on TCP 3203?
sudo ss -tlnp 'sport = :3203'
Linux: UDP 3203
sudo ss -ulnp 'sport = :3203'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3203
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3203 '
Windows (Command Prompt)
netstat -ano | findstr :3203
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3203 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3203
From Windows
Test-NetConnection HOST -Port 3203
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3203

Block port 3203 in the firewall

ufw
sudo ufw deny 3203/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3203 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3203 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3203' -Direction Inbound -Protocol TCP -LocalPort 3203 -Action Block
ufw
sudo ufw deny 3203/udp
iptables
sudo iptables -A INPUT -p udp --dport 3203 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3203 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3203' -Direction Inbound -Protocol UDP -LocalPort 3203 -Action Block

Related ports

3201cpq-tasksmart3202intraintra3204netwatcher-db3205isns

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