CRMCLink::Connect Method

Establishes a connection with a controller using the settings specified when the CRMCLink object was created (device type, port name, host name).

Syntax

C++

HRESULT Connect();

Return Value

Returns S_OK on success. Otherwise, an error code is returned. Possible error codes are listed below.

Remarks

This method is synchronous, which means that it will not return until the connection has been established, or the connection attempt fails, which may take several seconds to take place. If this method is called on the main thread, then the application will likely be unresponsive until this method completes. For applications where this is not acceptable, this and other synchronous methods should be called from a worker thread, and may use the CancelRequest method to cancel an in progress request.

WARNING: For Ethernet connections, it is highly recommended that the connection not be disconnected and re-connected between transactions. Doing so will have lower performance, and more importantly, each call to Connect() will consume a TCP connection in the Windows operating system. This TCP connection will not be fully released by the operating system until typically 2 minutes after Disconnect() is called. Therefore, it is possible to consume all available TCP connections by repeated calls to Connect()/Disconnect() and as a result be unable to re-connect over RMCLink or even adversely affect other applications running on the same PC.

Error Codes

Member Name	Description
E_OUTOFMEMORY	Out of memory.
RMCLINK_E_ALREADY_CONN	The link was already connected. To avoid this error, avoid calling Connect when the link is already connected. Use IsConnected if you are not sure if the connection is already made.
RMCLINK_E_SOCK_INTERNAL	Internal socket error.
RMCLINK_E_SOCK_CONN_FAIL	Unable to connect over TCP/IP to requested device.
RMCLINK_E_CANCELLED	Operation cancelled by call to CancelRequest.
RMCLINK_E_TIMEOUT	Operation timed out.
RMCLINK_E_SOCK_HOSTNAME_NOTIP	Host name did not resolve to an IPv4 address.
RMCLINK_E_SOCK_HOSTNAME_FAIL	Host name did not resolve.
RMCLINK_E_SOCK_GRACEFUL_CLOSE	TCP/IP connection closed by remote device.
RMCLINK_E_SOCK_ERROR_RD	Connection error while waiting for response from the remote device.
RMCLINK_E_SOCK_INV_RD_LEN	Connection error while waiting for response from the remote device.
RMCLINK_E_SOCK_ERROR_WR	Connection error while sending request to the remote device.
RMCLINK_E_SOCK_INV_WR_LEN	Connection error while sending request to the remote device.
RMCLINK_E_PORT_ACCESS_DENIED	Access to serial port denied. Verify not in use by another application.
RMCLINK_E_PORT_NOT_FOUND	Serial port not found.
RMCLINK_E_CE_IOE	Serial IOE error.
RMCLINK_E_CE_FRAME	Serial framing error.
RMCLINK_E_CE_BREAK	Serial Break error.
RMCLINK_E_CE_OVERRUN	Serial overrun.
RMCLINK_E_CE_RXOVER	Serial receive overrun.
RMCLINK_E_CE_RXPARITY	Serial parity error.
RMCLINK_E_CE_TXFULL	Serial transmitter full.
RMCLINK_E_CONN_BROKEN	Connection broken.
RMCLINK_E_PARTIAL_WRITE	Unable to send full request to the remote device.
RMCLINK_E_SOCK_HOSTNAME_INV	Invalid host name format.
RMCLINK_E_WRONG_CONTROLLER	Remote device is the wrong controller type.
RMCLINK_E_USB_NO_DRIVERS	Unable to access RMC USB driver. Please ensure that the driver has been properly installed.
RMCLINK_E_USB_DEV_NOT_FOUND	The controller with the specified DeviceId was not found on any USB port.
RMCLINK_E_USB_SETTIMEOUT	Internal USB driver error.
RMCLINK_E_USB_TXRXCLEAR	Internal USB driver error.
RMCLINK_E_USB_OP_ABORT	Unsuccessful transfer of data between the PC and the controller. Ensure that the physical connection between the PC and controller is still intact.
RMCLINK_E_USB_DISCONNECT	The controller appears to have been disconnected from the USB port. Ensure that the physical connection between the PC and controller is still intact.
RMCLINK_E_USB_UNK_FAILURE	The requested RMC is plugged into a USB port, but cannot be accessed. Ensure that no other applications are using this RMC. If the problem persists, try unplugging and re-plugging the USB cable to this controller and retry.
RMCLINK_E_USB_IN_USE	The requested RMC is plugged into a USB port, but cannot be accessed. Ensure that no other applications are using this RMC. If the problem persists, try unplugging and re-plugging the USB cable to this controller and retry.
RMCLINK_E_USB_NO_SETUPAPI	Unable to access operating system functionality for connecting to USB devices.

Example

The following code example illustrates the use of the Connect method.

C++

#include <windows.h>
#include <stdio.h>
#include "RMCLink.h"
 
void main()
{
    // In order to create COM objects, we must initialize the COM sub-system.
    ::CoInitialize(0);
 
    // Create a new RMCLink object.
    CRMCLink* pRMC = CRMCLink::CreateEthernetLink(CRMCLink::dtRMC70, _T("192.168.0.22"));
    if ( pRMC != NULL )
    {
        // Establish the connection.
        HRESULT hr = pRMC->Connect();
        if ( SUCCEEDED(hr) )
        {
            // Read F8:8 and F8:9 (Axis 0 Actual Position and Velocity)
            float afData[2];
            hr = pRMC->ReadFFile(CRMCLink::fn70StatusAxis0, 8, 2, afData);
            if ( SUCCEEDED(hr) )
            {
                printf("Actual Position = %.3f, Actual Velocity = %.3f\n",
                    afData[0], afData[1]);
            }
            // Close the connection.
            pRMC->Disconnect();
        }
 
        // Free the RMCLink object we created.
        delete pRMC;
    }
 
    // Release the COM sub-system.
    ::CoUninitialize();
}