Connection to Azure Synapse Analytics via HTTP Tunnel in ODBC Driver

Connecting to AzureSynapseAnalytics Using HTTP Tunneling

This section discusses how to connect the ODBC driver to AzureSynapseAnalytics through an HTTP tunnel. If you need to connect to AzureSynapseAnalytics in conditions of restricted connectivity, e.g. when a database server is hidden behind a firewall, or you need to transmit private network data through a public network, you can set up an HTTP tunnel to create a direct network link between two locations. The tunnel is created by an intermediary called a proxy server.

When AzureSynapseAnalytics server is hidden behind a firewall, the client is not able to connect to the server directly on a specified port. If the firewall allows HTTP connections, you can use the ODBC driver with a properly configured web server to connect to the database server. The driver supports HTTP tunneling based on the PHP script.

A possible scenario of using HTTP tunneling: the client needs to access the database of a website from a remote machine, but access to the designated port of the database server is forbidden — only connections on the HTTP port 80 are allowed. To establish a connection in this situation, you must deploy the tunnel.php script, which is distributed with the driver, on the web server. It enables access to the database server through an HTTP tunnel. The script must be accessible through HTTP. You can verify the script accessibility using any web browser. The script file is located in the "C:\Program Files (x86)\Devart\ODBC\AzureSynapseAnalytics\http\tunnel.php" folder. The web server must support PHP 5 or later.

To set up an HTTP tunnel, specify the connection parameters on the HTTP and HTTPS Options tab under Security Settings.

Connecting to AzureSynapseAnalytics Through HTTP Tunnel

HTTP Tunneling Options

Option	Description
`Use Http`	Enables HTTP tunneling.
`Http Url`	The URL of the PHP script for HTTP tunneling.
`Http User Name`	The username for the password-protected directory that contains the HTTP tunneling script.
`Http Password`	The password for the password-protected directory that contains the HTTP tunneling script.
`Http Trust Server Certificate`	Specifies whether to verify the server certificate during an SSL handshake. When `True`, the driver bypasses walking the certificate chain to verify the certificate. The default value is `False`.

Sample Connection String Using HTTP Tunneling

Connecting Through HTTP Tunnel and Proxy Server

The HTTP tunneling server may be not be directly accessible from the client machine. In this case, you need to additionally provide connection information for the proxy server.

Connecting to AzureSynapseAnalytics Through Proxy and HTTP Tunnel

Proxy Options

Option	Description
Proxy Host Name	The proxy hostname or IP address.
Proxy Port	The proxy port.
Proxy User Name	The proxy username.
Proxy Password	The proxy password.

Sample Connection String Using HTTP Tunneling and Proxy Server

Additional Information

There is one more way to tunnel network traffic. The Secure Shell forwarding, or SSH, can be used for data forwarding. However, SSH is designed to encrypt traffic rather than traverse firewalls. The Connecting via SSH document describes how to set up an SSH connection in the ODBC Driver for Azure Synapse Analytics.

Note that traffic tunneling or encryption increases the CPU and bandwidth usage. It is recommended that you use direct connection whenever possible.

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