Unable to connect to MS SQL Server using Go - sql-server

I am trying to connect to sql server express using go and this sql driver "github.com/denisenkom/go-mssqldb"
Currently it calls open then stalls on the ping command, it never pings or returns an error.
I am using winauth and it works with sql management studio.
I have verified the database name, if I put a false one in, an error is generated and logged at the open step.
I have tried setting a really short connection time out but the same thing happens.
I have tried connecting to a remote sql server and it works correctly.
The remote server is a developer version of sql server and had a name like xyz.abc.123 where my local sql express is called machine-name\sqlexpress.
Here is a sample program.
package main
import (
"database/sql"
_ "github.com/denisenkom/go-mssqldb"
"log"
)
func main() {
log.Println("Main:")
log.Println("Opening")
db, err := sql.Open("mssql", "server=Machine-Name\\SQLEXPRESS; database=MyDatabaseName;")
if err != nil {
log.Println("Open Failed: ", err.Error())
}
log.Println("Opened")
log.Println("Pinging")
err = db.Ping();
if err != nil {
log.Println("Failed to ping: ", err.Error())
}
log.Println("Pinged")
}

I encountered this same issue not too long ago and after two days of researching I was able to fix the issue.
The confusing aspect seems to come from the fact that the go-mssqldb needs a parameter passed named "server" and in SQL Management Studio they have a clear reference to server in the connection properties:
Connection Properties
However, this is not the value go-mssqldb is looking for. It is looking for the actual server where the DB is installed. Meaning, if it is installed in your local PC this would be "localhost". If it's on another machine in your network, then this would be the corresponding IP address or server name
Another thing to keep in mind is that go-mssqldb needs a port to connect to the DB and if you don't provide one, it assumes the port is 1433. However, mine wasn't that value. In order to look for your port number:
Open up SQL Server Configuration Manager.
Expand "SQL Server Network Configuration" on the tree on the left.
Click on "Protocols for SQLEXPRESS (or whatever name your DB has)"
In the main menu, make sure "TCP/IP" is enabled. If not, right-click on it and select "Enable".
Right-click on the "TCP/IP" again and select properties.
Select the "IP Addresses" tab and scroll all the way down.
Look at the section: "IPAll" and the number displayed in the "TCP Dynamic Ports" field is the correct port number.
SQL Server Configuration Manager
Finally, the command I ended up using to run my code ended up being:
sqlserver-agent -debug=true -server=localhost -port=62587 -user=Username -password=Password -database=DatabaseName

This https://code.google.com/p/odbc/ driver works with MS SQL Server for me.
Alex

Related

SQL Server 2012 not able to connect to named instance remotely with ssms

I'm running SQL Server 2012 on a Microsoft Windows Server 2012 R2. I am running a named instance called PP. The server authentication is set to "SQL Server and Windows Authentication mode".
When I am logged into the server via Remote Desktop I can log in to the named instance via SSMS just fine using a using a SQL Server username and password. When I try to log into the named instance remotely using the same username and password I get an error as described in this screenshot (my reputation isn't high enough to paste the screenshot directly in my post, please follow the link):
Here are the things I have checked so far:
I can ping the IP Address of the remote server from my local computer and get successful responses.
I have configured the instance of SQL Server to accept remote connections as described in this article.
In SQL Server Configuration Manager on the remote server under the protocols for my named instance I have enabled "Shared Memory", "Named Pipes" and "TCP/IP".
Under "TCP/IP" properties on the remote server in SQL Server Configuration Manager in the "IP Addresses" tab under the "IP2" section I have set the "TCP Dynamic Ports" value to blank. I have tried setting the "TCP Port" value to 1433 and then to 1434 (the difference between a regular instance and a named instance) and going through the rest of the steps below as shown in the screenshot here (these are the values specified in the article I linked to above)
Windows firewall is not running on the remote server, and from what I can see there is not another firewall running on the remote server either.
The SQL Server Browser service on the remote server has been stopped and restarted.
After I have made all of these changes and verified all of these settings the SQL Server service for the named instance on the remote server has been stopped and restarted.
After all of this I am still getting my original error when I try to connect to the named instance of SQL Server on my remote server from my local computer via SSMS. I've been searching high and low and cannot find any additional troubleshooting steps to diagnose this problem. Will someone please point me in the direction of the next steps I should take to fix this? Thanks in advance.
I logged off and then came back the next day to implement the suggestions in #Andrey Nikolov 's answer and for some reason I am able to connect remotely to the named instance now. The settings that ended up working for the "IP2" section of the "TCP/IP" configuration for the named instance are the "TCP Dynamic Ports" value is set to blank and the "TCP port" is set to 1433. I didn't make any other changes. The rest of the configuration is as I noted in my OP. I have sysadmin access to this server but I'm not the actual administrator so I guess it's possible that the actual administrator might have changed something else between when I logged off and then logged back on but I don't know what that might be. Thanks to #Andrey Nikolov for your input.
EDIT:
This issue came back in full force a few days later for no reason that I could determine. After a long search I found a very informative MS Doc that goes through the whole troubleshooting process for this in depth, hope this helps someone else confronted with this. Here's the link:
https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/troubleshoot-connecting-to-the-sql-server-database-engine?view=sql-server-2017
It says it's for SQL Server 2017 but I was able to follow it to fix my SQL Server 2012 issue. For my situation it turns out that because I had 2 separate instances of MS SQL on my server the initial instance was using all of the default settings as described elsewhere and my instance I was trying to connect to was using a completely different port. Using this Doc I was able to find out what port my instance is using and specify that in the "Server name" box of SSMS when I tried to connect. Now it works like a charm.
I think your named instance TCP/IP isn't configured properly. In case you connect locally it does not connect using TCP/IP, but using shared memory. You set your instance to listen on port 1434, but this port is used by SQL Browser service and most likely the SQL Server engine service can't open the port (you can confirm that by finding the error in the logs). To make it work you should set IP2 -> TCP Dynamic Ports to be 0 and clear IP2 -> TCP Port. Configured like this, your named instance will use dynamic ports. If you want to configure it to use specific port, replace 1434 in IP2 -> TCP Port with available port number.

SQL Server connection string windows 7 and windows 10 - Named Pipes Provider, error 40 [duplicate]

I can't seem to connect to my database from a site. I get this error:
Named Pipes Provider, error: 40 - Could not open a connection to SQL Server
I tried using the local IP address to connect as well as a public one. I've tried:
Yes, the site can communicate with the server
Named pipes/TCP is enabled.
Remote connections are allowed.
Windows Firewall is off
Created an exception for port 1433 in Windows Firewall.
Enabled everything in SQL Server Configuration Manager.
What else can I do here?
Solving this problem is very easy:
Go to control panel.
search for services.
Open Local services window from your search results
Restart your MSSQLSERVER service.
Screenshot of the steps:
And the simplest solution - check if your slash is back...
I spent about an hour trying to figure out what's wrong with SERVER/INSTANCENAME when everything is configured correctly, named pipes, user access rights... and suddenly it struck me, it's not a slash, it's a backslash (\).
The horror, the shame...
It's a three step process really after installing SQL Server:
Enable Named Pipes
SQL Config Manager --> SQL Server Network Consif --> Protocols --> Named Pipes --> Right-click --> Restart
Restart the server
SQL Config Manager --> SQL Server Services --> SQL Server (SQLEXPRESS) --> Right-click --> Restart
Use proper server and instance names (both are needed!)
Typically this would be .\SQLEXPRESS, for example see the screenshot from QueryExpress connection dialog.
There you have it.
I had just installed SQL SERVER 2012 developer. When I was creating my first SSIS package, I received this pipes error when I was trying to create a data connection task in SQL Server 2012 Data Tools in the Connection Manager box. I resolved with the help of the post above.
If choose a named instance and you call your named instance SSQDatabase1 and your pc's name is PCX1. You must enter PCX1\SSQDatabase1 not just SSQDatabase1
or you will receive the named pipes error.
A thread on MSDN Social, Re: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server, has a pretty decent list of possible issues that are related to your error. You may want to see if any of them could be what you're experiencing.
Incorrect connection string, such as using SqlExpress
Named Pipes(NP) was not enabled on the SQL instance
Remote connection was not enabled
Server not started, or point to not a real server in your connection string
Other reasons such as incorrect security context
try basic connectivity tests between the two machines you are working on
i Just enabled TCP/IP,VIA,Named Pipes in Sql Server Configuration manager , My problem got solved refer this for more info Resolving Named Pipes Error 40
Use SERVER\\ INSTANCE NAME .Using double backslash in my project solved my problem.
Thanks to Damian...
TCP/IP
Named Pipes
... both enabled
Web Config....(for localhost)
<add name="FooData" connectionString="Data Source=localhost\InstanceName;Initial Catalog=DatabaseName;Integrated Security=True;" providerName="System.Data.SqlClient" />
Did have the same problem. Spent like 6 hours when had to migrate some servers.
Tried all suggestions available on this topic and others.
Solution was as simple as server restart!
Very simple solution
use (local)\InstanceName
that's it. it worked for me.
TL;DR; Your SQL Server instance is using dynamic ports which is not working. Force SQL Server to use static port # 1433.
Complete Details: First of all this problem is more likely if you've a mix of default and named instance or named instances only(which was my case).
Key concept: Each instance of Microsoft SQL Server installed on a computer uses a different port to listen for incoming connection requests. Default instance of SQL Server uses port # 1433. As you install named instances then they will start using dynamic ports which is decided at the time of start-up of Windows service corresponding to named SQL Server instance.
My code was failing (with error code 40) to connect to the only named SQL Server instance that I had on my VM. You can try below possible solutions:
Solution # 1: Client code trying to connect to SQL Server instance takes help from SQL Server browser service to figure out port number at which your named instance is listening for incoming connections. Make sure SQL browser service is running on your computer.
Solution # 2: Check the port # (in yellow color) your named SQL Server instance is using from SQL Server configuration manager as shown in the snapshot below:
Use that port number explicitly in your connection string or with sqlcmd shown below:
sqlcmd -s mymachinename,11380 -i deleteDB.sql -o SQLDelete.txt
Solution # 3: Force your named instance to use port # 1433 which is used by default instance. Remember this will work only if you don't have any default SQL Server instance on your computer as the default SQL Server instance would be using using port # 1433 already. Same port number can't be uses by two different Windows services.
Mark TCP Dynamic ports field to blank and TCP Port field to 1433.
Change the port number in your connection string as shown below:
sqlcmd -s mymachinename\instanceName -i deleteDB.sql -o SQLDelete.txt
OR
sqlcmd -s mymachinename,1433 -i deleteDB.sql -o SQLDelete.txt
Note: Every change in TCP/IP settings requires corresponding Windows service restart.
Interestingly enough after resolving the error when I went back to dynamic port setting to reproduce the same error then it didn't happen. Not sure why.
Please read below interesting threads to know more about dynamic ports of SQL Server:
How to configure SQL Server Port on multiple instances?
When is a Dynamic Port “dynamic”?
When to use a TCP dynamic port and when TCP Port?
I got leads to solution of my problem from this blog.
in my case, i had a standalone server, i changed the sql server port default port 1433 in configuration manager to some number and restarted the sql serve service to take effect,i was able to connect to the sql server through management studio if i login to the server. but i was not able to connect from my local machine through sql server, i was getting the error:
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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 5)
I checked and verified all the below
-Named pipes/TCP is enabled.
-Remote connections are allowed.
-Windows Firewall is off
-Created an exception for portin Windows Firewall( this was not necessary in my case as the server is in same subnet network).
-Enabled everything in SQL Server Configuration Manager.
then i chnaged back the port number to default 1433 and restarted the sql server service, and the issue got resolved and i am able to connect the sql server from my local management studio.
I had the same problem. I use the MSSQL Server Management Studio 2017 and solved this problem using these steps:
Check for working fine SQL Server Services services or not.
Also check for working in good condition SQL Server (MSSQLSERVER).
Also check for working fine SQL Server Browser.
Restart SQL Server (MSSQLSERVER)
and fixed it.
You will find most likely your DB name is not correct, you will see the server name in VS like "DESKTOP-0I14BKI" but if you open up SSMS you will see DESKTOP-0I14BKI\SQLBLAHBLAH , simply add "\SQLBLAHBLAH" (instance name) to your "server name" in VS connection properties.
You will see:
To Fix:
Try the following steps:
Open Services window (open "run box" and type services.msc).
Looking for SQL services (with SQL prefix).
Start them (if cannot start. Goto step 4).
Right_click to each service -> Properties -> Change to tab "Log on"-> choise log on as "Local ..." -> 0K. Then start SQL services again.
Try Open SQL and connect database.
In my case,
I opened SQL Server Management Studio and searched for SQLEXPRESS in my Database engine.
It had two instances and I selected the correct one.
If you are working with Asp.net core and using appsettings.json than write server as localhost and after write sql instance name for enabled named pipe like this
"ConnectionString": {
"dewDB": "server=localhost\\dewelopersql;database=dewdb;User ID=sa;password=XXXXX",
},
After following all the steps mentioned here, if it still does not connect, try adding the DNS with the IP address in the hosts file in the etc folder. Adding an IP address instead of DNS name in the connection string should be a temporary solution to check if the connection actually works.
I tried using the local IP address to connect as well as a public one.
I've tried:
Yes, the site can communicate with the server Named pipes/TCP is
enabled. Remote connections are allowed. Windows Firewall is off
Created an exception for port 1433 in Windows Firewall. Enabled
everything in SQL Server Configuration Manager.
i ensured and did the above as well and I just want to share that the DOUBLE BACKSLASH
oBuilder.DataSource = "SPECIFICPCNAME\SQLEXPRESS";
Using a SINGLE BACKSLASH resulted into a build error i.e.: Error 1 Unrecognized escape sequence
I hope this helps the next guy - I've sacrificed dinner, midnight snack and NBA highlights time solving this (shame)
Thanks to [Tamizh venthan]
^_^
Enable TCP/Ip , Piped Protocol by going to Computer Management ->SQL and Services, ensure the Service is On. Enbale the port on the Firewall. Try to login through Command Prompt -> as Admin; last the User Name
should be (local)\SQLEXPRESS. Hope this helps.
Open SQL Server Configuration Manager
Select SQL Server Services from right.
Find your server from right and go to its properties (with right click)
Change log on method to Local System.
I had the same problem and solved the problem by disabling my firewall(ESET).
The first step to solve this problem should be to try pinging your own computer from another computer. If you have firewall on, you may not be able to ping yourself. I tried pinging my own pc, then ping was failed(didnt get response from the server)
I was trying to add a new connection in VS2015. None of the suggestions here worked. Suspecting some sort of a bug in the wizard, especially since SSMS was able to connect just fine, I decided to try and trick it. It worked!
Instead of adding the connection, use "Create new SQL Server Database". Enter your server name and a random name for the new DB, e.g. "test".
Assuming this succeeds, open Server Explorer in VS, locate the connection in Data Connections, right-click it and select Modify Connection.
Change "test" (from step 1) to the name of the existing database you want to connect to. Click "Test Connection". This time it should work!
Delete the temporary database you created in step 1.
I have one more solution, I think.
I recently had changed my computer name so, after I couldn't connect still after trying all above methods.
I changed the Server name..
Server name => (browse for more) => under database engine, a new server was found same as computers new name.
This worked, and life is good again.
I struggled for ages on this one before I realized my error - I had used commas instead of semicolons in the connect string
I had this issue but none of the suggestions above fixed it.
I was seeing this issue when I deployed my website to IIS. The fix was to go into advanced settings against the default app pool and change the identity property from the default to Administrator.
For me it was a Firewall issue.
First you have to add the port (such as 1444 and maybe 1434) but also
C:\Program Files (x86)\Microsoft SQL Server\90\Shared\sqlbrowser.exe
and
%ProgramFiles%\Microsoft SQL Server\MSSQL12.SQLEXPRESS\MSSQL\Binn\SQLAGENT.EXE
The second time I got this issue is when I came back to the firewall, the paths were not correct and I needed to update form 12 to 13! Simply clicking on browse in the Programs and Services tab helped to realise this.
Finally, try running the command
EXEC xp_readerrorlog 0,1,"could not register the Service Principal Name",Null
For me, it returned the error reason
I tried pretty much everything on this page but I had some underlying issues which were actually what needed to be resolved. I was unable to do certain things like open SQL Server Configuration Manager, which ended up being corrupt/missing WMI provider files.
There are lots of tedious ways to resolve this issues according to what I've read, but the tool from tweaking.com was able to remove and replace/repair my WMI (Windows Management Instrumentation) Provider files.
I used to do computer repair and overall the tweaking.com tool really impressed me, and it was suggested from one of the WMI error forum pages I went to.
After I fixed this issue I was able to connect to my SQL db, both locally and remotely.
Hope this helps someone.
open port number 1433 on your server for sql remote connection
If you tried restarting the MSSQLSERVER service, and it did not work, this might be a solution:
If you are using SQLExpress, your server name should be as the following ComputerName\SQLExpress. However, for SQLDeveloper, you do not have to right SQLDeveloper after your ComputerName.

Cannot connect to SQL Server named instance

I cannot connect to a named instance of SQL Server. I am trying to connect to domain\named_instance but this happens to all servers I try to connect to apart from localhost
The error that I cam getting looks like this:
So far I have tried:
Enabling remote connections in SQL Server
Enabling TCP/IP in the SQL Server Configuration Manager
Changing all the TCP ports in SQL Server Configuration Manager to 1433
I also tried running the command below where the number is the Process ID of the SQL Server Service:
netstat -ano | find /i “7608”
My result was as follows:
As suggested by this website.
However I do not get the ESTABLISHED return only the 2 LISTENING ones.
My IP2 IP address is set to: 192.168.2.176not 100% sure if this is right or not.
I cannot (due to security issues with my hosting company) get the IP of the server. Any and all suggestions are welcome!
I am in dire straits, and really need help!
I am using SQL Server 2008
Since you are stating you are trying to use named pipes (can be seen in the screenshots) I think you errornously trying to use TCP configuration to do this.
You need to need to enabled SQL to listen named pipes. How to do - see here.
There are multiple types of error "Cannot connect to 'Server Name'".
These error are differentiated on the basis of Error Additional Information.
One of the Solution for above error is
Connect the server using Windows Authentication.
Right Click on the Server(i.e. first option) in Object Explorer. Then go to Properties.
Go to Security then select Server Authentication as "SQL Server and Windows Authentication Mode"
Again Right Click on the Server(i.e. first option) in Object Explorer. Then select restart.
Then try again login using SQL Authentication

Diagnosing Connection to SQL Server

I'm trying to create an ODBC connection to SQL Server, but when i do, i get error:
Connection failed:
SQLState: '01000'
SQL Server Error: 10060
[Microsoft][ODBC_SQL Server Driver][TCP/IP Sockets] COnnectionOpen (Connect()).
Connection failed:
SQLState: '08001'
SQL Server Error: 17
[Microsoft][ODBC_SQL Server Driver][TCP/IP Sockets] SQL Server does not exist or access denied.
Here's what I've tried:
not a firewall issue: tried with firewall on SQL Server turned off, and client turned off. Also able to telnet 1433 from client and that works fine.
not an access issue: I can login from many different computers, including the SQL Server itself using the account i'm using on client (using SQL Server authentication)
i can ping the hostname and IP address. (i've tried both)
The only thing i can think of is that the client computer is windows server 2003, and has various roles setup:
File Server
Application Server
Terminal Server
Domain Controller
DNS Server
I don't know why these services are setup, but for the time being i can't shut them off. Would it be any of these, and if so, is there a way to disable any of the aspects of them, that might be blocking SQL.
Any advise truly appreciated!
Found the issue. For some reason, even though SQL was not in use on the client, it was installed, and by going to All Programs -> Microsoft SQL Server -> Client Network Utility, i found that the protocal TCP/IP was using port 4717. I have no idea why that port was in use, and even further, i'm not sure why it would even matter - I was just setting up an odbc connection, and not using sql server (on the client) at all. Either way, I changed this to the typical port (1433), and like boom, ODBC connection works like charm!
Is it possible that the server in question has not been configured to use named pipes?
CAUSE
The most common reason that this connection attempt failed is
that this DSN or ODBC data source attempted to make a connection using
the TCP/IP sockets Net-Library, which is Dbmssocn.dll. Because the SQL
Server is not listening for incoming connections for TCP/IP sockets
clients, the connection fails. From ISQL/w, the second error message
stated above would be returned. The OS Error is 10061, and the
function call that failed was ConnectionOpen(connect()).
WORKAROUND
By default, SQL Server will listen for incoming connections
made by Named Pipes clients. Named Pipes is the default IPC mechanism
for clients to connect to a SQL Server version 4.2, 6.0, and 6.5
server. The Named Pipes DLL is Dbnmpntw.dll, and it should be located
in the Windows\System or Winnt\System32 directory. The TCP/IP sockets
netlib DLL is Dbmssocn.dll, and also should be in the Windows\System
or Winnt\System32 directory.The most common resolution to this problem
is to configure the client computer to connect using Named Pipes.
Configuring Named Pipes If the Microsoft Data Access Components (MDAC)
ODBC drivers have been installed on the computer, you can make this
change in the second step of the Create New Data Source wizard.
NOTE: You can download MDAC drivers from:
http://msdn2.microsoft.com/en-us/data/aa937730.aspx To configure the
client, start the Create New Data Source wizard, click the Client
Configuration button, and perform the following steps, based on the
version of the SQL Server ODBC driver you are using:
For SQL Server ODBC Driver version 3.50
Click the Net Library tab and use the drop down list box to set the
default network (Net Library) to Named Pipes.
On the Advanced tab, remove any advanced entries that reference the
server you are connecting to.
Click Done.
For SQL Server ODBC Driver version 3.70
In the Network Libraries section of the Edit Network Library Configuration
dialog box, select Named Pipes.
Click OK.
If you do not have the MDAC ODBC drivers installed, you can use the
SQL Server Client Configuration Utility tool to set the default
Net-Library to Named Pipes. You can install the client utilities from
the SQL Server CD from the i386 directory.
Source: http://support.microsoft.com/kb/195566
By default SQL Native Client seems to look for MSSQLSERVER instance. However, if you use SQLEXPRESS all connections through that will fail.
Very strange, but try installing your SQL Server with MSSQLSERVER instance name - it should work!
To create a new Data source to SQL Server, do the following steps:
In host computer/server go to Sql server management studio --> open Security Section on left hand --> right click on Login, select New Login and then create a new account for your database which you want to connect to.
Check the TCP/IP Protocol is Enable. go to All programs --> Microsoft SQL server 2008 --> Configuration Tools --> open Sql server configuration manager. On the left hand select client protocols (based on your operating system 32/64 bit). On the right hand, check TCP/IP Protocol be Enabled.
In Remote computer/server, open Data source administrator. Control panel --> Administrative tools --> Data sources (ODBC).
In User DSN or System DSN , click Add button and select Sql Server driver and then press Finish.
Enter Name.
Enter Server, note that: if you want to enter host computer address, you should enter that`s IP address without "\\". eg. 192.168.1.5 and press Next.
Select With SQL Server authentication using a login ID and password entered by the user.
At the bellow enter your login ID and password which you created on first step. and then click Next.
If shown Database is your database, click Next and then Finish.
Adding another check point to all the above answers. Valid if you are using a named instance of Sql Server ( ServerName\InstanceName)
Make Sure UDP Port is enabled in Windows Firewall with SQL Server Default UDP Port
Number 1434. If not present create a new incoming rule in Firewall for UDP 1434 Port and restart SQL Server Browser Services in SQL configuration Manager.

Connecting to SQL Server Named Instance from Windows 64bit

I have both java and .net applications running on an app server using Microsoft Windows Server 2003, Enterprise Edition. These are being migrated to another app server Windows 2008 64-bit machine.
All applications connect to the same SQL Server 2005 database, on a named instance.
So far I have tried to move the applications exactly as they are, with no changes in the configuration files, from the old box to the new box.
On the new app server, neither the java nor the .net applications connect to the database (named instance).
JDBC error message: "The connection to the named instance has failed. Error: java.net.SocketTimeoutException: Receive timed out."
The .net error message: "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible."
If I change the DB config to one that is not on a named instance it works on the new app server.
The database is setup correctly, because we were able to connect on the old app server. I can ping the database server from the new app server.
Is there any reason this won't work on the new app server?
java connection string: "jdbc:microsoft:sqlserver://[dbservername];SelectMethod=Cursor;instanceName=[dbinstance]"
.net connection string: "Server=[dbservername]\[dbinstance];Database=Risk_DB;Uid=[user];Pwd=[pwd];"
UPDATE
Per suggestions in the answers, I got the instance port number. I also installed SQL Server Management Studio so I can eliminate my apps as the problem points. From Management Studio, if I use [servername][instancename], I get the message "a network-related or instance-specific error while establishing a connection to SQL Server..." But it works when i use [servername],[port]. Not sure if there's anyway to work around this?
UPDATE #2 Escalated the issue to the infrastructure/server/network team. They disabled windows firewall on the new app server. Presto, now I can connect to [dbservername]\[dbinstance] in Management Studio, and all apps are working using existing configuration files.
Your named instance is going to be running on a different port. Port 1433 (the default for a default instance) is probably open, and the port that the named instance is running on is probably blocked. You can check the port in the error log for the named instance (assuming you can connect locally, in Object Explorer, expand the server, expand Management, expand SQL Server Logs, right-click current, and choose "View SQL Server Log" IIRC), it will say something like this on startup:
Server is listening on [ 127.0.0.1 <ipv4> 3587 ].
That last number is the port number that needs to be accessible from your remote machine and whatever network devices and services it has to go through to get there. If you don't find a line like that, it's possible that TCP/IP is not enabled for the named instance. On that server, go to SQL Server Configuration Manager, expand SQL Server Network Configuration, click on "Protocols for " and make sure TCP/IP is enabled in the right pane. If you have to enable this you'll need to restart SQL Server for it to take effect.
If it is already enabled (or once you enable it and restart the service), you should be able to refresh this view and validate the port that is being used if you right-click TCP/IP, hit properties, and move to the IP Addresses tab. You can see the ports currently being for each IP. Here there will be multiple IPn sections and an IPAll section. For each IP, you can change the "TCP Port" box to a port you want to use (and delete any values in all the "Dynamic TCP Ports" box to 0). Hit Apply and restart the service. This will again require a restart of the service but will allow you to specify a specific port so you can add an exclusion to your firewall (or make use of one that already exists, assuming this server isn't already using that port).
Possible issues:
Firewall maybe blocking connections.
The instance name is not the same as specified in the connection string.
The connection string specifies a different port or SQL Server is running on a different port rather than the default 1433

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