First, you must set RemoteHost and RemotePort properties to specify other control, with which you will communicate using UDP.

Second, when you want to get all sent data, you do not need to specify nBytesTotal in GetData method. Instead, in your case, use:

this.GetData(@lcData)

Using nBytesTotal causes Winsock to truncate all other received data and may cause loss of information in your case.

See MSDN article "Using the Winsock Control" for more information.