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.