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Siemens SINUMERIK Controller
Communication · Intermediate · 30-120 minutes
Siemens 840D 100921 - Remote diagnostics: Waiting for connection to port
Alarm 100921 indicates the remote diagnostics function is attempting to establish a connection but is waiting for a response on the specified network port. This is typically an informational message rather than a critical fault, occurring when remote service personnel initiate a VPN or direct connection to the control system. The alarm persists until the connection handshake completes or times out.
100921
Siemens 840D 100921 - Remote diagnostics: Waiting for connection to port
Remote diagnostics: Waiting for connection to port
Siemens SINUMERIK operator message 100921: Remote diagnostics: Waiting for connection to port. This is an informational message from the SINUMERIK control indicating a system status or operation result that may require operator action.
Root Cause Summary
Alarm 100921 indicates the remote diagnostics function is attempting to establish a connection but is waiting for a response on the specified network port. This is typically an informational message rather than a critical fault, occurring when remote service personnel initiate a VPN or direct connection to the control system. The alarm persists until the connection handshake completes or times out.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Identify the port number displayed in the alarm message (parameter %1) - common ports are 102, 8080, or custom ports configured for remote access.
- 2
Check the facility firewall and router settings to ensure the specified port is open for incoming TCP connections to the control IP address.
Coordinate with IT department before modifying firewall rules to maintain network security policies.
- 3
Verify Windows Firewall settings on the PCU (if applicable) by navigating to Control Panel > Windows Firewall > Advanced Settings and checking inbound rules for the port.
- 4
Test port accessibility using network diagnostic tools (ping, telnet, or port scanner) from the remote service location to confirm connectivity.
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Always verify with your machine manual or a certified technician before performing service procedures.