read Causes Freezing?

Hey all. I'm currently writing a basic TCP client script with basic write and read functions implemented. As I understand, it makes sense to enter an infinite while loop to read responses from the server until read returns zero (in which case break; is sent to break out of the while loop). It makes sense in theory. But, whenever read can't find any bytes to read, it just freezes up my program (I assume until it's given bytes to read). So, is there a way to avoid this? I want to use the infinite while loop technique, but it won't work because instead of returning zero or -1 for error, it just freezes everything.

Thanks in advance.

I'm currently trying this:

Code:

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while((n = read( sockfd, buffer, 200)) > 0)
        {
                //n = read( sockfd, buffer, 200);
                //if(n == 0 || n == -1) exit(1);
                if(n > 0) buffer[n] = 0;
                printf( buffer );
                printf("%d", n);
                if(n < 1) exit(1);
        }

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One way is to use the select() call to determine if there's anything available before you try and read it.
Select has the ability to return after a timeout.

Quote:

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Originally Posted by Salem

One way is to use the select() call to determine if there's anything available before you try and read it.
Select has the ability to return after a timeout.

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So, is read supposed to cause freezing like this? Because, I've been reading tutorials and checking source code all day and I see everyone using the infinite while loop until read returns 0.

Well the read will block until there's something to read, or the other end closes the connection.

The other way would be to make the socket non-blocking, then deal with the return values of -1 AND an errno value of EAGAIN.

Could you tell me how to make the socket non-blocking?

Quote:

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Originally Posted by Masna

Could you tell me how to make the socket non-blocking?

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Code:

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#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>

// for fcntl which "stops" the blocking of blocking functions:
#include <fcntl.h>
#include <unistd.h>

int main(void)
{
int mysocket;
if( (mysocket = socket(AF_INET, SOCK_STREAM, 0) == -1) return printf("Bye.");
fcntl(mysocket, F_SETFL, O_NONBLOCK);
// some more code...
}

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BTW, your code is containing many errors.