Port1503— Windows Live Messenger
T.120 protocol port for multimedia conference data transmission
Registry assignments, software defaults and local listeners are different things. A port number alone does not identify or secure a service.
Software Using This Port (1 software)
Community software entries: links are references, not individual verification.
Windows Live Messenger
Windows Live Messenger instant messaging
Usage Suggestions
- Before using port 1503, please confirm it is not occupied by other services
- If you encounter port conflicts, consider using other ports or stopping the occupying service
Frequently asked questions
What is port 1503 used for?
Port 1503 sits in the System category. This page lists the registered purpose and the software commonly associated with it; to see what is actually listening on a specific machine, check the process with ss/netstat.
Is port 1503 TCP or UDP?
The registered protocol on this page is TCP. The same number behaves independently on each protocol: TCP may be listening while UDP is idle, so check them separately.
How do I check if port 1503 is in use?
On Linux: sudo ss -tlnp 'sport = :1503' for an exact port match. On macOS: sudo lsof -nP -iTCP:1503 -sTCP:LISTEN. On Windows PowerShell: Get-NetTCPConnection -LocalPort 1503 -State Listen. A listener counts as confirmed only when you can see the bind address and process name; without root/admin you will not see other users' processes.
Is port 1503 secure? Should I open it in my firewall?
A port number has no inherent security — it depends on whether the listening service is correctly configured and whether it needs exposure at all. Keep loopback/internal-only services firewalled; where public access is required, pair it with source restrictions, VPN or authentication.
Quick Info
- Port
- 1503
- Protocol
- TCP
- Categories
- System
- Usage Status
- 1 software in use
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