Why does "server" always unexpectedly generate continuous dialogues?

[R0ck1n]

I started a llamacpp server for chatting. But its response for one prompt consisted of a whole conversation.
I expected:

1. Send a question to server through HTTP POST
2. Server respond an answer
3. repeat 1&2
   The procedure should be like these:
   [send request]User: Hello
   [response]AI: Hi, can I help you?
   [send request]User: Yeah, I met a problem that...
   [repsonse]AI: I understood that...

However, it worked like:

1. Send a question to server through HTTP POST
2. return a series of answers and questions that it generated automatically, till the end of the conversation.
   That is to say:
   [send request]User: Hello
   [response]AI: Hi, can I help you? User: Yeah, I met a problem that... AI: I understood that... User: Thank you. Bye. AI: Welcome, Bye.

When I used "main" and -i parameter, it worked exactly like my expectation. Meanwhile, I also noticed if I pressed Enter, it would generate the conversation continuously including both questions and answers.

What's the essential issue? And can it be addressed? Thanks a lot!