Reading from a socket until certain character is in buffer

Question

I am trying to read from a socket into a buffer until a certain character is reached using read(fd, buf, BUFFLEN).

For example, the socket will receive two lots of information separated by a blank line in one read call.

Is it possible to put the read call in a loop so it stops when it reaches this blank line, then it can read the rest of the information later if it is required?

If I have correct interpretation of your problem,you wanna display the first lot of info then idle a couple of seconds for the next one? — jasonkim, Feb 22 '12 at 16:33

hmjd · Accepted Answer · 2012-02-22T16:24:18.203

4

A simple approach would be to read a single byte at a time until the previous byte and the current byte are new-line characters, as two consecutive new-line characters is a blank line:

size_t buf_idx = 0;
char buf[BUFFLEN] = { 0 };

while (buf_idx < BUFFLEN && 1 == read(fd, &buf[buf_idx], 1)
{
    if (buf_idx > 0          && 
        '\n' == buf[buf_idx] &&
        '\n' == buf[buf_idx - 1])
    {
        break;
    }
    buf_idx++;
}

Any unread data will have to be read at some point if newly sent data is to be read.

edited Feb 22 '12 at 16:24

answered Feb 22 '12 at 16:09

hmjd

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A character at a time was my initial thought as well, but I'm having difficulty getting it to read it one at a time: inline ` int rlen; int i = 0; while ((rlen = read(proxyFd, &buf[i], 1)) > 0) { if (strstr(&buf[0], "\n\n")) { printf("bingo\n"); break; } i += rlen; } ` – DMcB1888 Feb 22 '12 at 16:21
@DMcB1888, you only ever comparing the first two characters in `buf` to `"\n\n"` as you use `buf[0]`. Try `strstr(&buf[i - 1], "\n\n")` but **make** sure `i > 0`. – hmjd Feb 22 '12 at 16:26

score 0 · Answer 2 · answered Feb 22 '12 at 16:10

You still need to read from the socket if you want to access this information later, otherwise it will be lost. I think best implementation would be to keep looping reading from the socket, while another process/thread is launched to perform any operation you want when a blank like is received.

Reading from a socket until certain character is in buffer

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