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Port 4803 (notateit, notateit-disc)

IANA assigns port 4803 to notateit, notateit-disc: Notateit Messaging.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
notateit TCP Notateit Messaging - -
notateit-disc UDP Notateit Messaging Discovery Ean Black -

Registry dates for this port: registered 2009-04-08.

Check what is listening on port 4803

Linux: is anything listening on TCP 4803?
sudo ss -tlnp 'sport = :4803'
Linux: UDP 4803
sudo ss -ulnp 'sport = :4803'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4803
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4803 '
Windows (Command Prompt)
netstat -ano | findstr :4803
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4803 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4803
From Windows
Test-NetConnection HOST -Port 4803
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4803

Block port 4803 in the firewall

ufw
sudo ufw deny 4803/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4803 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4803 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4803' -Direction Inbound -Protocol TCP -LocalPort 4803 -Action Block
ufw
sudo ufw deny 4803/udp
iptables
sudo iptables -A INPUT -p udp --dport 4803 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4803 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4803' -Direction Inbound -Protocol UDP -LocalPort 4803 -Action Block

Related ports

4801iwec4802ilss4804aja-ntv4-disc4827htcp

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