Remote access to a named instance

I try to connect from a pc to a SQL Server on another pc. Both pc’s are in a workgroup. I want to connect from a Windows Forms application to a named instance on the other computer. By now I have been able to connect from one pc to SQL Server on the other with tcp:smurfin, 52782.

I want to be able to use servername\instancename (instead of portnumber) to make a connection in a Windows Forms application.

I’ve checked / tried te following:
• In the properties of the instance, tab Connections, the option Allow Remote Connections is enabled
• In Configuration Manager: TCP is enabled
• The service SQL Server Browser is started
• On the tab IPAddresses, in the section IPAll, there is NO portnumber for TCP Port. And TCP Dynamic Ports has the nummer 52782
• I have created un inbound rule for port 52782 and also for 1434 (SQL Server Browser). And to be on the save side: a rule for 1433 as well.
• Restarted the service

If I run the following code in SQL Server, that same port number (52782) is returned:

EXEC xp_ReadErrorLog 0, 1, N'Server is listening on', N'any', NULL, NULL, 'DESC'

GO
SELECT local_tcp_port
FROM sys.dm_exec_connections
WHERE session_id = @@SPID
GO

What else can I do?

post your connection string.

Password=password;Persist Security Info=True;User ID=user;Initial Catalog=databasename;Data Source=tcp:servername, 52782.

I want it to be

Password=password;Persist Security Info=True;User ID=user;Initial Catalog=databasename;Data Source=servername\instancename.

if you use a non-standard port (not 1433) I think you will always need to put it in the connstr