The send command has been changed so that it does not time out after 5 seconds, but instead waits indefinitely for a response. Specify the -async option if you do not want to wait for a result. You can also specify an alternate display with the -displayof option. Chapter 40 describes send starting on page 562.
The name of an application can be set and queried with the new tk appname command. Use this instead of winfo name ".".
Because of the changes in the send implementation, it is not possible to use send between Tk 4.0 applications and earlier versions.