What does Windows error code 7011 (ERROR_CTX_MODEM_RESPONSE_ERROR) mean?

ERROR_CTX_MODEM_RESPONSE_ERROR

The modem did not accept the command sent to it. Verify that the configured modem name matches the attached modem.

ERROR_CTX_MODEM_RESPONSE_ERROR is Win32 error 7011 (0x00001B63) in legacy Remote Desktop Services and Terminal Services session handling.

What to verify

Verify whether the attached modem accepts the command sequence for the configured model. Check exact command and sanitized response, modem model and firmware, and serial port settings.

Likely causes

• the selected modem profile sends unsupported commands.
• the serial connection uses incorrect settings.
• the modem is in an unexpected command state.
• firmware or driver behavior does not match the profile.

Troubleshooting steps

1. Collect exact command and sanitized response.
2. Record modem model and firmware.
3. Correlate serial port settings with TerminalServices operational logs, session and user-configuration records, device or modem diagnostics, and the caller’s connection trace.

Handling, retry, and recovery

Reset the modem, select the correct profile, and verify the command sequence outside the user callback path before retrying.

Related errors

ERROR_CTX_MODEM_RESPONSE_TIMEOUT means no response arrived; this code means a response indicated rejection or error

Example

A generic profile sends an initialization command unsupported by the attached modem. Selecting the vendor-specific profile changes the command sequence and the callback proceeds.

References

• Microsoft: Win32 system error range containing this code
• Microsoft: Remote Desktop Services API
• Microsoft: WTS configuration classes
• Microsoft: WTSAPI32 reference