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Port 2703 (sms-chat)

IANA assigns port 2703 to sms-chat: SMS CHAT.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sms-chat TCP SMS CHAT - -
sms-chat UDP SMS CHAT - -

Check what is listening on port 2703

Linux: is anything listening on TCP 2703?
sudo ss -tlnp 'sport = :2703'
Linux: UDP 2703
sudo ss -ulnp 'sport = :2703'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2703
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2703 '
Windows (Command Prompt)
netstat -ano | findstr :2703
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2703 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2703
From Windows
Test-NetConnection HOST -Port 2703
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2703

Block port 2703 in the firewall

ufw
sudo ufw deny 2703/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2703 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2703 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2703' -Direction Inbound -Protocol TCP -LocalPort 2703 -Action Block
ufw
sudo ufw deny 2703/udp
iptables
sudo iptables -A INPUT -p udp --dport 2703 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2703 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2703' -Direction Inbound -Protocol UDP -LocalPort 2703 -Action Block

Related ports

2701sms-rcinfo2702sms-xfer2704sms-remctrl2705sds-admin

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