Smbc can send and receive WinPopup messages, but this function works as frontend. Samba Team doesn't include in libsmbclient library functions to send and receive WinPopup messages. To send messages you must first configure Smbc. You must "smbclient" parameter sets in "~/.smbc/smbcrc"; for example
smbclient /usr/bin/smbclient
If you want to receive WinPopup messages you must set "message command" parameter in "smb.conf" file; for example
message command = /path_to/smbc -m 'message from %f on %m' -i %s; rm %s
At this time Samba after receiving a WinPopup message executes Smbc and Smbc saves received message to temporary directory. If you run Smbc at the same time when message is received it is immediatelly displayed; if not, message will be displayed after you run Smbc.