C sockets - randomly receiving more than one string at a time

I have encountered an interesting C sockets problem.

I am receiving incoming strings and noticed that I will, randomly, receive 3 strings at a same time for the first 2 ~ 4 strings.

For example, I am receiving the following incoming strings.

1~message~i love you\r\n
2~message~do you love me?\r\n
3~message~when are we going to meet again?\r\n 
4~message~How about now?\r\n
5~message~Oh! I'm pregnant!\r\n

I added a counter to track the number of messages received and noticed that the counter sometimes does not count the first 3 strings. For example

1~message~i love you\r\n
->Line 1 received
2~message~do you love me?\r\n
3~message~when are we going to meet again?\r\n
4~message~How about now?\r\n
->Line 2 received
5~message~Oh! I'm pregnant!\r\n
->Line 3 received

The following开发者_JAVA技巧 is my code for printing the line number

int lineNo = 1;
while ((recvBytes = recv(clntSockfd, buffer, sizeof(buffer), 0)) > 0) {
    printf("%s", buffer);
    memset(&buffer, 0, sizeof(buffer));
    printf("Line %d received\n", lineNo++);
}

I'm not sure why is this happening since this problem did not appear when i coded in Java nio.

Any ideas, folks?

Assuming you are using TCP, relating recv() calls to "messages" (or "lines") in your case is flawed. TCP, conceptually, is a stream of bytes. The sending operating system is free to group multiple send() calls into a single IP packet, as is the receiving operating system free to report multiple incoming packets as a single recv() call (assuming the buffer is large enough). It may even choose to split an incoming packet across recv calls.

So you really need to put a message structure in the data itself, eg. by scanning for line breaks in the data received.

That this didn't occur in Java was pure luck.

You are not reading till end of line. The buffer can contain more than one line.

what connection type are you using?

UDP is unreliable most of the time.

TCP is much better than UDP in terms of reliability.