Service bus connection is not working from on-premise console application - timeout

Question

I have created a .net core 3.1 console application for reading azure service bus queue messages and deployed the EXE in a client on-premise VM. It was working initially but now it is not working from VM (now also working from local machine). I am getting a time-out (socket exception) while executing the exe in on-premise VM. I am using shared access policy connection strung to connect the service bus.
Exception :
Azure.Messaging.ServiceBus.ServiceBusException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. ErrorCode: TimedOut (ServiceCommunicationProblem)
---> System.Net.Sockets.SocketException (10060): A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
at Microsoft.Azure.Amqp.Transport.TransportStream.EndRead(IAsyncResult asyncResult)
at Microsoft.Azure.Amqp.Transport.TransportStream.<>c__DisplayClass22_0.b__1(IAsyncResult a)
at System.Threading.Tasks.TaskFactory1.FromAsyncCoreLogic(IAsyncResult iar, Func2 endFunction, Action1 endAction, Task1 promise, Boolean requiresSynchronization)

Answer 1

The most common connection issue in an enterprise environment is that the ports needed for AMQP over TCP (5671/5672) are not open. Changing the transport to AMQP over WebSockets often helps, as it will use port 443 and may be routed through a proxy, if needed.
Both the transport and the proxy (if needed) can be specified using the ServiceBusClientOptions when creating your client:
var options = new ServiceBusClientOptions
(
TransportType = ServiceBusTransportType.AmqpWebSockets,
WebProxy = new WebProxy("https://proxyserver:80", true)
};
var client = new ServiceBusClient("<< CONNECTION STRING >>", options);
For more information, you may want to look at the Service Bus troubleshooting guide.