I was unable to connect to MySQL 5 on port 3307

Database is hosted on mysql5.mydomain.co.uk on port 3307. I am using mysql5, PHP 5.1.4 & mysqli
I could connect to my database using MySQL Admin using the above hostname & port, with the same username, password & dbname

When I attempted to connect with CI using mysql5.mydomain.co.uk:3307 as the hostname I got the error message:
  Message: mysqli_connect() [function.mysqli-connect.php]: (HY000/2005): Unknown MySQL server host ‘mysql5.mydomain.co.uk:3307’ (11004)

Leaving off the port suffix gave:
  Message: mysqli_connect() [function.mysqli-connect.php]: (28000/1045): Access denied for user ‘xxxxx’@‘85.13.212.2’ (using password: YES)

Eventually fixed this by adding $db[‘mydb’][‘port’] to /config/database.php and amending mysqli_driver.php as below:

  function db_connect()
  {
      return @ mysqli_connect($this->hostname, $this->username, $this->password, $this->database, $this->port);
  }

Hope this is helpful to others

Adding the port to the database config file needs to done for the release version.  I had a similar issue (I run two different mysql instances on different ports on the same machine).

Intercept, I did exactly the same, earlier spending like 2 hours looking for the cause of the problem.  I think CI should have “port” variable in the database config file by default.