The error 'memcached address family not supported by protocol' typically occurs when Memcached is unable to connect to its server. The most common cause is that the IP address or port number provided for the server is incorrect or in a format that is not recognized by the protocol. Another cause could be that the version of Memcached being used is not compatible with the operating system or network configuration.
To resolve the 'memcached address family not supported by protocol' error, start by verifying that the IP address and port number specified for the Memcached server are correct and formatted properly. Additionally, ensure that your version of Memcached is compatible with your operating system and network configuration.
If the issue persists, try changing the IP address of the server to its hostname or vice versa. This can help to ensure that the IP address is in the correct format and resolved correctly. You may also try using the telnet command to connect to the Memcached server and verify that it is running and accepting connections.
Finally, if none of these solutions work, consider upgrading to a newer version of Memcached that is compatible with your system or configuring your network settings to be compatible with the current version.