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Port 2203 (b2-runtime)

IANA assigns port 2203 to b2-runtime: b2 Runtime Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
b2-runtime TCP b2 Runtime Protocol - -
b2-runtime UDP b2 Runtime Protocol - -

Check what is listening on port 2203

Linux: is anything listening on TCP 2203?
sudo ss -tlnp 'sport = :2203'
Linux: UDP 2203
sudo ss -ulnp 'sport = :2203'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2203
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2203 '
Windows (Command Prompt)
netstat -ano | findstr :2203
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2203 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2203
From Windows
Test-NetConnection HOST -Port 2203
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2203

Block port 2203 in the firewall

ufw
sudo ufw deny 2203/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2203 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2203 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2203' -Direction Inbound -Protocol TCP -LocalPort 2203 -Action Block
ufw
sudo ufw deny 2203/udp
iptables
sudo iptables -A INPUT -p udp --dport 2203 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2203 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2203' -Direction Inbound -Protocol UDP -LocalPort 2203 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.