What I. Communications Link Failure: Com.Mysql.Jdbc.Exceptions.Jdbc4.CommunicationsExceptions The Difference Between Live And Extract Connections
want my database to communicate with my java programs Can anyone provide me with a sample program using JDBC?
I’m getting an error ”com.mysql.cj.jdbc.exceptions.communicationsexception: communications link failure” while doing the same.
Regarding com mysql cj jdbc exceptions communicationsexception communications link failure If you get a SQLException: Connection refused or Connection timed out or a MySQL specific CommunicationsException: Communications link failure, then it means that the DB isn't reachable at all. This can have one or more of the following causes: IP address or hostname in JDBC URL is wrong.Hostname in the JDBC URL is not recognized by the local DNS server.
Port number is missing or wrong in the JDBC URL.
DB server is down.
DB server doesn't accept TCP/IP connections.
DB server has run out of connections.
Something in between Java and DB is blocking connections, e.g. a firewall or proxy.
To solve the one or the other, follow the following advices:
Verify and test them with ping.
Refresh DNS or use IP address in JDBC URL instead.
Verify it based on my.cnf of MySQL DB.
Start the DB.
Verify if mysql is started without the --skip-networking option.
Restart the DB and fix your code accordingly so that it closes connections in finally.
Disable firewall and/or configure firewall/proxy to allow/forward the port.