blocked on read/recv / how to read/send proper buffers

**fudgecode** · 11-02-2010

hello forum,

i am somehow stuck with a beginner networking problem. i generally do not know how to read/recv all data to process it. for instance, taking this example:

Code:

file = open("test.txt",O_RDONLY);
while(read(file,buf,1)>=0){
       strncat(store,buf,1);
}

now, if i would replace the strncat line with

Code:

send(client,buf,1,0);

the while loop finishes and the program ends like it should. with the strncat in place it reads the file but is somehow stuck in the while loop. i wonder what i do wrong there.
possibly i have generally a wrong way of trying to read a buffer with recv/read wrong, possibly somebody can show me what the correct way is to read/send a full buffer. lets say
i have a defined buffer of 1024 bytes but the file is 4094 big.

thank for your answers,
fc

**Salem** · 11-02-2010

> read(file,buf,1)>=0
Have you thought about RTFM - On success, the number of bytes read is returned (zero indicates end of file)

Unless you have

Code:

char buf[2] = { 0, 0 };

your strncat is a disaster waiting to happen.
In any event, it is an UGLY way of solving the problem.

Code:

char buf[BUFSIZ];
while ( (r=read(file,buf,BUFSIZ)) > 0 ) { // read until EOF or error
  char *bp = buf;
  do {
    w = send(client,buf,r,0);
    if ( w <= 0 ) break;
    r -= w;  // reduce the amount left to send
    buf += w;  // what remains to be sent
  } while ( r > 0 ); // keep going until it's all sent
}

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