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Port 2103 (zephyr-clt)

IANA assigns port 2103 to zephyr-clt: Zephyr serv-hm connection.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
zephyr-clt TCP Zephyr serv-hm connection - -
zephyr-clt UDP Zephyr serv-hm connection - -

Check what is listening on port 2103

Linux: is anything listening on TCP 2103?
sudo ss -tlnp 'sport = :2103'
Linux: UDP 2103
sudo ss -ulnp 'sport = :2103'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2103
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2103 '
Windows (Command Prompt)
netstat -ano | findstr :2103
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2103 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2103
From Windows
Test-NetConnection HOST -Port 2103
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2103

Block port 2103 in the firewall

ufw
sudo ufw deny 2103/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2103 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2103 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2103' -Direction Inbound -Protocol TCP -LocalPort 2103 -Action Block
ufw
sudo ufw deny 2103/udp
iptables
sudo iptables -A INPUT -p udp --dport 2103 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2103 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2103' -Direction Inbound -Protocol UDP -LocalPort 2103 -Action Block

Related ports

2101rtcm-sc1042102zephyr-srv2104zephyr-hm2105minipay

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