Containers cannot talk each other

[dave7]

I have two containers: ASP.NET Core app (name: DockerApp) and an MSSQL Server (name: DockerSQLServer). They are on the same custom network (name: backend).
But when DockerApp tries connect to the DockerSQLServer it encounters an error:

Unhandled exception. Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 35 - An internal exception was caught)

The connection string is correct, I suppose: Server=DockerSQLServer,1433;Database={database};MultipleActiveResultSets=true;User Id=sa;Password={password}

If I do the same in Windows 10 Docker, it works well.

 

[Rusty]

I have two containers: ASP.NET Core app (name: DockerApp) and an MSSQL Server (name: DockerSQLServer). They are on the same custom network (name: backend).
But when DockerApp tries connect to the DockerSQLServer it encounters an error:

Unhandled exception. Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 35 - An internal exception was caught)

The connection string is correct, I suppose: Server=DockerSQLServer,1433;Database={database};MultipleActiveResultSets=true;User Id=sa;Password={password}

If I do the same in Windows 10 Docker, it works well.

Do you get the same error with Server=NASIPADDRESS?

 

[dave7]

Do you get the same error with Server=NASIPADDRESS?

No, I don't.
Additional information, the DockerSQLServer was created like this:
docker run -d --name DockerSQLServer--network=backend --restart=unless-stopped -v sqlvolume:/var/opt/mssql -e "ACCEPT_EULA=Y" -e "SA_PASSWORD={password}" -e "MSSQL_PID=Express" -p 1434:1433 -d mcr.microsoft.com/mssql/server:2019-latest

 

[Rusty]

So it is able to talk to your sql when using the ip address?

 

[dave7]

So it is able to talk to your sql when using the ip address?

Yes, it is. But only on port 1434.

 

[Rusty]

Yes, it is. But only on port 1434.

Well ofc. That’s the port sql container is running on your nas. What other port did you expect?

 

[dave7]

Well ofc. That’s the port sql container is running on your nas. What other port did you expect?

Right, I shouldn't expect other port. But I assume that DockerApp should be able to connect to DockerSQLServer inside the Docker on port 1433. Or am I wrong?

 

[Rusty]

should be able to connect to DockerSQLServer inside the Docker on port 1433

But you mapped it to 1434. Try and connect App docker container to your SQL 1434 port.

 

[dave7]

But you mapped it to 1434. Try and connect App docker container to your SQL 1434 port.

I tried with port 1434 before. It didn't work that way either.

 

[Rusty]

Ok so it works with IP address on port 1434?

 

[dave7]

Ok so it works with IP address on port 1434?

Yes, but it doesn't with container name.

 

[Rusty]

Well docker internal DNS is probably working fine, so this leaves port problem (doubt it considering they are in the same isolated network) or something that's more likely and that would be SQL configuration.

Would suggest to try enabling both named pipes and tcpip in sql server or set and configure a host file on your APP container that will point a name of your choice for that SQL container to its IP address. See if that will help.

This is a common problem when it comes to SQL instance resolution (named pipes and tcpip).

SQL Server clients may change protocols - SQL Server

This article describes that client computers that have MDAC version 2.6, or later, can try multiple protocols or IPC mechanisms to establish connections to SQL Server.

docs.microsoft.com

 

[dave7]

Well docker internal DNS is probably working fine, so this leaves port problem (doubt it considering they are in the same isolated network) or something that's more likely and that would be SQL configuration.

Would suggest to try enabling both named pipes and tcpip in sql server or set and configure a host file on your APP container that will point a name of your choice for that SQL container to its IP address. See if that will help.

This is a common problem when it comes to SQL instance resolution (named pipes and tcpip).

SQL Server clients may change protocols - SQL Server

This article describes that client computers that have MDAC version 2.6, or later, can try multiple protocols or IPC mechanisms to establish connections to SQL Server.

docs.microsoft.com

Thx for te help.
"Would suggest to try enabling both named pipes and tcpip in sql server "
How could i do this in the container? I dont't find any solution.

 

[Rusty]

Thx for te help.
"Would suggest to try enabling both named pipes and tcpip in sql server "
How could i do this in the container? I dont't find any solution.

Running it via CLI should run. Powershell command/script could work. Consult some links and methods discussed here.

Enable tcp\ip remote connections to sql server express already installed database with code or script(query)

I am deploying sql express with my application. I will like that database engine to accept remote connections. I know how to configure that manual by launching the sql server configuration manager,

stackoverflow.com