SQL Server SQLState = 08001 NativeError = 2 while establishing connection

Question

I am newbie to SQL Server. I am using SQL Server 2008. I have a procedure named proc_generate_excel_with_columns. The procedure takes the database name, table name and Excel file path as input parameters.

The procedure picks data from the specified SQL Server table, and puts it into a dummy file and finally copies the contents of the dummy file into the specified Excel file.

When I run the procedure, I get the following error.

SQLState = 08001 NativeError = 2
Error = [Microsoft][SQL Server Native Client 10.0] A network related or instance specific error has occurred while establishing connection to SQL Server. Server is not found or not accessible. Check if the instance name is correct and is SQL server is configured to allow remote connections.

The procedure code is as follows.

create procedure [dbo].[proc_generate_excel_with_columns]
(
    @db_name    varchar(100),
    @table_name varchar(100),   
    @file_name  varchar(100)
)
as
    --Generate column names as a recordset
    declare @columns varchar(8000), @sql varchar(8000), @data_file varchar(100)

    select 
        @columns = coalesce(@columns + ',', '') + column_name + ' as ' + column_name 
    from 
        information_schema.columns
    where 
        table_name = @table_name

    select 
        @columns = '''''' + replace(replace(@columns, ' as ', ''''' as '), ',',',''''')

    --Create a dummy file to have actual data
    select 
        @data_file = substring(@file_name, 1, len(@file_name) - charindex('\', reverse(@file_name))) + '\data_file.xls'

    --Generate column names in the passed EXCEL file
    set @sql='exec master..xp_cmdshell ''bcp " select * from (select '+@columns+') as t" queryout "'+@file_name+'" -S "SBHATT6440" -c -T'''

    exec(@sql)

    --Generate data in the dummy file
    set @sql='exec master..xp_cmdshell ''bcp "select * from '+@db_name+'..'+@table_name+'" queryout "'+@data_file+'" -S "SBHATT6440" -c -T'''
exec(@sql)

--Copy dummy file to passed EXCEL file
set @sql= 'exec master..xp_cmdshell ''type '+@data_file+' >> "'+@file_name+'"'''
exec(@sql)

--Delete dummy file 
set @sql= 'exec master..xp_cmdshell ''del '+@data_file+''''

This is the image of SQL Server Services

This is the image of Protocols for SQLEXPRESS

Any help is greatly appreciated. I can provide any extra information if required.