Lesson 6: Add synchronization to your application

Lesson 5: Build and run your application

UltraLite User's Guide
Tutorial: Build an Application Using the C++ API

Lesson 6: Add synchronization to your application

UltraLite applications exchange data with a consolidated database. In this lesson, you add synchronization to the simple application you created in the previous section. In addition, you change the output to verify that synchronization has taken place.

Adding synchronization actually simplifies the code. Your initial version of main.cpp has the following lines, that inserts some data into your UltraLite database.

productTable.SetProd_id( 1 );
productTable.SetPrice( 400 );
productTable.SetProd_name( "4x8 Drywall x100" );
productTable.Insert();

productTable.SetProd_id( 2 );
productTable.SetPrice( 3000 );
productTable.SetProd_name( "8' 2x4 Studs x1000" );
productTable.Insert();

This code is included to provide an initial set of data for your application. In a production application, you would usually not insert an initial copy of your data from source code, but would carry out a synchronization.

To add synchronization to your application

Add a synchronization information structure to your code.
- Add the following line immediately after the line that says // (2) declare variables.
```
auto ul_synch_info synch_info;
```
  This structure holds the parameters that control the synchronization.
Replace the explicit inserts with a synchronization call.
- Delete the productTable methods listed above.
- Add the following lines in their place:
```
conn.InitSynchInfo( &synch_info );
synch_info.user_name = UL_TEXT( "50" );
synch_info.version = UL_TEXT( "custdb" );
synch_info.stream = ULSocketStream();
synch_info.stream_parms = 
   UL_TEXT("host=localhost");
conn.Synchronize( &synch_info );
```
  The value of 50 is the MobiLink user name.
  
  The string custdb instructs MobiLink to use the default script version for synchronization.
  
  ULSocketStream() instructs the application to synchronize over TCP/IP, and host=localhost specifies the host name of the MobiLink server, which in this case is the current machine.
Compile and link your application.
- Select Build > Build APITutorial.exe to compile and link the executable. Depending on your settings, the APITutorial.exe executable may be created in a Debug directory within your APITutorial directory.
Start the MobiLink server running against the sample database.

From a command prompt in your APITutorial directory, enter the following command:
```
start dbmlsrv9 -c "dsn=UltraLite 9.0 Sample"
```
Run your application.

From the Build menu, choose Execute APITutorial.exe.

The application connects, synchronizes to receive data, and writes out information to the command prompt window. The output is as follows:
```
The ULData object is open
Price: 400
Price: 3000
Price: 40
Price: 75
Price: 100
Price: 400
Price: 3000
Price: 75
Price: 40
Price: 100
```

In this lesson, you have added synchronization to a simple UltraLite application.