SQL Connectivity Issue From Cloud app to on-prem server

Santhi Dhanuskodi 165 Reputation points


I have deployed a .net core MVC app in azure app service as a webapp.

I have to connect to a on-prem sql server to retrieve data. I have setup Azure relay/hybrid connection for the same. Also I have installed hybrid connection manager in on-prem server.

I get SQL connectivity issues intermittently. Either of these 3 errors. All these exceptions are occuring inconsistently. I have enabled TCP/IP already in the server.

A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.)

Connection Timeout Expired. The timeout period elapsed while attempting to consume the pre-login handshake acknowledgement. This could be because the pre-login handshake failed or the server was unable to respond back in time. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=121; handshake=59896;

Login failed for user '<userid>'.

We cannt see any logs from SQL server which are useful for this.

I suspect its more of Relay/hybrid connection issue. how do i troubleshoot this? What could be the causes? Where can we see additional logs for hybrid connection?

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  1. Bruce (SqlWork.com) 57,891 Reputation points

    because you are using a proxy, the logs are not going to tell you much. aside from the timeout, there are no errors as far as the proxy is concerned.

    you will probably need to run a network trace between the on-prem client and the Sqlserver. an outgoing trace from the on-prem client to the azure proxy will tell you if you are getting connection / traffic issues.

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  2. MikeyQiao-MSFT 655 Reputation points Microsoft Vendor

    Hi,Santhi Dhanuskodi

    We haven't received a response from you for some time, and I would like to know the status of your issue. The issue may be caused by TLS. Please refer to the following documentation.


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