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Open [LJM User's Guide]

Opens a desired LabJack and associates a device handle number (connection ID).  The device handle may then be passed as an input to other functions.


int DeviceType,
int ConnectionType,
const char * Identifier,
int * Handle)


DeviceType [in]

An integer containing the type of the device to be connected:

LJM_dtANY (0) - Open any supported LabJack device type

LJM_dtT4 (4) - Open a T4 device

LJM_dtT7 (7) - Open a T7 device

LJM_dtT8 (8) - Open a T8 device

LJM_dtTSERIES (84) - Open any T-series device

LJM_dtDIGIT (200) - Open a Digit-series device

For other LabJack devices, see What driver/library should I use with my LabJack?

ConnectionType [in]

An integer containing the type of connection desired:

LJM_ctANY (0), LJM_ctUSB (1), LJM_ctTCP (2), LJM_ctETHERNET (3), LJM_ctWIFI (4)

Other UDP options:


Also, LJM_ctANY_UDP (11) is available in LJM 1.2100 and later.

Other TCP or UDP options:


Identifier [in]

A string that may identify the device to be connected.  To open any device, use LJM_idANY (or the string "ANY").  To specify an identifier, use a serial number, IP address, or device name.  See Identifier Parameter for more information. If you don't have a device available, you can use LJM_DEMO_MODE (or the string "-2") to open a fake device.

Handle [out]

The new handle that represents the device connection.


LJM errorcode or 0 for no error.

Related Functions

LJM_Open and LJM_OpenS are essentially the same, except that LJM_OpenS uses string parameters for DeviceType and ConnectionType rather than integer parameters.

See LJM_GetHandleInfo to retrieve information about a handle.

See LJM_ListAll or LJM_ListAllS to find multiple devices.


See the notes in Opening and Closing.

When the ConnectionType parameter of this function is network-based, this function will check the IP addresses listed in LJM_SPECIAL_ADDRESSES_FILE.


Open a LabJack T7

int LJMError;
int handle;
LJMError = LJM_Open(LJM_dtT7, LJM_ctANY, "ANY", &handle);
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