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B.6.2.10 Communication Errors and Aborted Connections

If connection problems occur such as communication errors or aborted connections, use these sources of information to diagnose problems:

If the server has the log_error_verbosity system variable set to 3, you might find messages like this in your error log:

[Note] Aborted connection 854 to db: 'employees' user: 'josh'

If a client is unable even to connect, the server increments the Aborted_connects status variable. Unsuccessful connection attempts can occur for the following reasons:

If these kinds of things happen, it might indicate that someone is trying to break into your server! If the general query log is enabled, messages for these types of problems are logged to it.

If a client successfully connects but later disconnects improperly or is terminated, the server increments the Aborted_clients status variable, and logs an Aborted connection message to the error log. The cause can be any of the following:

Other reasons for problems with aborted connections or aborted clients:

  • The max_allowed_packet variable value is too small or queries require more memory than you have allocated for mysqld. See Section B.6.2.9, “Packet Too Large”.

  • Use of Ethernet protocol with Linux, both half and full duplex. Some Linux Ethernet drivers have this bug. You should test for this bug by transferring a huge file using FTP between the client and server machines. If a transfer goes in burst-pause-burst-pause mode, you are experiencing a Linux duplex syndrome. Switch the duplex mode for both your network card and hub/switch to either full duplex or to half duplex and test the results to determine the best setting.

  • A problem with the thread library that causes interrupts on reads.

  • Badly configured TCP/IP.

  • Faulty Ethernets, hubs, switches, cables, and so forth. This can be diagnosed properly only by replacing hardware.

See also Section B.6.2.8, “MySQL server has gone away”.

User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
  Posted by Rainer Franke on February 28, 2012
I searched long time to find a possible solution for "Aborted connection 'number' to db: 'dbname' user: 'username' host: 'hostname' (Got an error reading communication packets)".
Webapplication is Typo3.
I think this information can also help to understand a possible Problem
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