Can read() function on a connected socket return zero bytes?

linux sockets tcp network-programming runtime-error
kumar picture kumar · Mar 10, 2010 · Viewed 40.4k times · Source

I know that read() is a blocking call unless I make the socket non-blocking. So I expect read() call which requests 4K of data should return a positive value ( no of bytes read) or -1 on error ( possible connection reset by client etc). My question is: Can read() return '0' on any occasion?

I am handling the read() this way:

   if ((readval = read(acceptfd, buf, sizeof(buf) - 1)) < 0)
    {

    }
    else
    {
       buf[readval] = 0;
       //Do some thing with data  
    }

This code bombs if read() return zero and I know how to fix it. But is it possible for read() to return zero?

Answer

user184968 picture user184968 · Mar 10, 2010

When a TCP connection is closed on one side read() on the other side returns 0 byte.

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