Connect to the server.
Overrides FileTransfer::connect
function connect() {
$parts = explode(':', $this->hostname);
$port = count($parts) == 2 ? $parts[1] : $this->port;
$this->connection = new MockTestConnection();
$this->connection->connectionString = 'test://' . urlencode($this->username) . ':' . urlencode($this->password) . "@{$this->host}:{$this->port}/";
}