From Xojo Documentation
Sends a message consisting of command and data to the group specified by groupName.
Effective with 2017r3, the command parameter is Int32 instead of Integer to prevent incorrect behavior in 64-bit apps.
The text encoding is not sent to the other application. So if you want to preserve text encoding, you should use ConvertEncoding to e.g. UTF-8 before sending the string and use DefineEncoding when you receive a message to restore the text encoding.