# SimConnect_Open<no value>
The **SimConnect\_Open** function is used to send a request to the *Microsoft Flight Simulator* server to open up communications with a new client.

 

##### Syntax

``` cpp
HRESULT SimConnect_Open(
    HANDLE*  phSimConnect,
    LPCSTR  szName,
    HWND  hWnd,
    DWORD  UserEventWin32,
    HANDLE  hEventHandle,
    DWORD  ConfigIndex
    );
```

 

##### Parameters

<table><thead><tr class="header"><th>Parameter</th><th>Description</th><th>Type</th></tr></thead><tbody><tr class="odd"><td><em>phSimConnect</em></td><td>Pointer to a handle to a SimConnect object.</td><td>Integer</td></tr><tr class="even"><td><em>szName</em></td><td>Pointer to a null-terminated string containing an appropriate name for the client program.</td><td>Integer</td></tr><tr class="odd"><td><em>hWnd</em></td><td>Handle to a Windows object. Set this to NULL if the handle is not being used.  

<em>UserEventWin32</em></td><td>Integer</td></tr><tr class="even"><td><em>UserEventWin32</em></td><td>Code number that the client can specify. Set this to 0 if it is not being used.</td><td>Integer</td></tr><tr class="odd"><td><em>hEventHandle</em></td><td>A Windows Event handle. A client can be written to respond to Windows Events, rather than use a polling and callback system, which can be a more efficient process if the client does not have to respond very frequently to changes in data in Microsoft Flight Simulator.</td><td>Integer</td></tr><tr class="even"><td><em>ConfigIndex</em></td><td>The configuration index. The <code>SimConnect.cfg</code> file can contain a number of configurations, identified in sections with the <code>[SimConnect]</code> or <code>[SimConnect.N]</code> titles. Setting this configuration index indicates which configuration settings to use for this SimConnect client. This is useful for applications that communicate with a number of different machines that are running <em>Microsoft Flight Simulator</em>. The default configuration index is zero (matching a <code>[SimConnect]</code> entry in a <code>SimConnect.cfg</code> file). Note the E_INVALIDARG return value.</td><td>Integer</td></tr></tbody></table>

 

##### Return Values

The function returns an **HRESULT**. Possible values include, but are not limited to, those in the following table.

{{< table-wrapper >}}

| Return value  | Description                                                                                                     |
|---------------|-----------------------------------------------------------------------------------------------------------------|
| S\_OK         | The function succeeded.                                                                                         |
| E\_FAIL       | The function failed.                                                                                            |
| E\_INVALIDARG | A SimConnect section in the `SimConnect.cfg` file did not contain the config index requested in the parameters. |

{{< /table-wrapper >}}


 

##### Example

``` cpp
HRESULT hr; HANDLE hSimConnect = NULL;  
hr = SimConnect_Open(&hSimConnect, "Your Application Name", NULL, 0, 0, SIMCONNECT_OPEN_CONFIGINDEX_LOCAL);
```

 

##### Remarks

Most client applications will have one [SimConnect\_Open](simconnect-open/) call, and one corresponding [SimConnect\_Close](simconnect-close/) call. However in some applications, multiplayer in particular, multiple [SimConnect\_Open](simconnect-open/) calls may be necessary, in which case an array or list of handles will need to be maintained, and closed appropriately.

 

A client can optionally examine the [SIMCOMMENT\_RECV\_OPEN](../structures-and-enumerations/simconnect-recv-open/) structure that is returned after a call to [SimConnect\_Open](simconnect-open/). This structure gives versioning and build information that should be useful when multiple versions of SimConnect and multiple versions of *Microsoft Flight Simulator* that support it, are available.

If a remote client successfully establishes a link with Flight Simulator, but at some later time the network connection is lost, SimConnect functions will return the `NTSTATUS` error `STATUS_REMOTE_DISCONNECT` (0xC000013CL).

 

The [SIMCONNECT\_EXCEPTION\_VERSION\_MISMATCH](../structures-and-enumerations/simconnect-exception/) exception will be returned if a versioning error has occurred, typically when a client built on a newer version of the SimConnect client dll attempts to work with an older version of the SimConnect server. If this exception is received the number 4 is returned in the *dwIndex* parameter of the [SIMCONNECT\_RECV\_EXCEPTION](../structures-and-enumerations/simconnect-recv-exception/) structure.