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Support Article

Message blocked error occurs after migrating to AMP 5.7.21



Message blocked error occurs after migrating to AMP 5.7.21 Server (Business Gateway). This behavior is observed only in the AMP 5 Server compatibility mode with AMP 4 client.

Error Messages (ERR=0x0002000c=0:512:12) General error: (ERR=0x000100cd=0:256:205) Message blocked
. com.vaultus.vmsserver.core.sync.ServerPeerConnection.sendMessage(
... 17 more

Steps to Reproduce

  1. Upgrade from AMP 4.3.x Server (Business Gateway) to AMP 5.7.21 Server (Business Gateway)
  2. Log in to the AMP 5 server with AMP 4 client.
  3. Start a sync with amount of messages that exceed the configured or the default window size.
  4. Turn the device network connection off.

Root Cause

The Message Blocked error was a result of exceeding the window size (the number of Sent and Not Acknowledged messages) while sending messages to an AMP 4.3 client.


Configuring the Message Send and Receive window size in the compatibility mode was added in the AMP 5.7.22. In the compatibility mode, the number of messages that AMP Business Gateway retains in the queue to be sent to the device without receiving ACKs, can be controlled. Configuring these parameters prevents messages from being blocked due to temporary network issues.

Both the Message Send and Receive window size can be configured in the COMM section within the
cluster.config configuration file:

Published November 8, 2017 - Updated October 8, 2020

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