I'm testing a softphone with blind transfer function and I am really satisfied with it. I have downloaded the sample program provided by Ozeki VoIP SIP SDK and as I have Visual Studio 2010 on my computer, I could run the program immediately.
To implement the blind transfer was an easy task, it can be done with a simple method call and giving the phone number as a parameter. In the sample, the call was transferred to a hardcoded number but I could implement a more sophisticated solution as well.
I just needed to add the transfer button and the event handler which performs the actual transfer. This code shows the event handler method for the Transfer button. To blind transfer a call I only needed to specify the number I transfer the call to and call the transfer method of the call object.
1. private void btnBlindTransfer_Click(object sender, EventArgs e)
3. string transferTo = tbBlindTransfer.Text.Trim();
4. if (string.IsNullOrEmpty(transferTo))
During the transfer the call state was Transferring and when the transfer was successful, the softphone exited the call and the other two parties could communicate with each other.
As for the remote party, during the transfer, it was set to hold and it got back to the call when the transfer was completed. In this case the communication was continued with the third party. When the transfer could not be done the communication was set back with the original communication peer.
So I have positive experiences with this sample program and it was a good starting point for my project. You can check it if you google this: voip-sip-sdk.com/p_351-voip-blind-transfer-voip