Please help - how send message

[Анатолий Стяпшин]

Hello, can you give me some advice - i am using nullclient and i want
to send message to user right after it was received by my program.
I want to send user some text, maybe even his own text.
As i can see function "null_write_conv" if for receiving  messages
from user. But i cant't figure it out - what function i should use to
send messages to user, what is it's name.
Can you help me with advice, and sorry for my bad english :)