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copied!<p>Non-blocking writes don't work how you're expecting them to.</p> <p>If the write can't be completed immediately, write() returns to your code - but it <strong>doesn't</strong> keep trying to send the data in the background. All it does is say "I couldn't write at the moment - try again later". It does this by returning -1, with <em>errno</em> set to EAGAIN.</p> <p>Also, remember that when successful, write() returns the <em>number of bytes successfully written</em>. So if you're getting a return value of 1 when you asked for 2 bytes to be written, that means it was only partially successful, and you need to call write() again some time for the second byte.</p> <p>Basically, if you're using non-blocking IO, you want your txbytes() function to call write() in a loop until either your buffer is empty, or it returns -1. If it returned -1 you need to check errno - if it's EAGAIN, you'll have to call write() again some other time; anything else is probably a real error. Something like this:</p> <pre><code>ssize_t written = 0; while (oBufLength > 0 && written > -1) { size_t i; printf("about to transmit %d bytes: ", oBufLength); for(i = 0; i < oBufLength; i++) { printf(" %u",oBuf[i]); } printf("\n"); written = write(BAMid, oBuf, oBufLength); printf("Write returned %d\n", written); if (written > 0) { /* The first "written" number of bytes in the buffer have now been sent, so * we discard them and move up the remaining bytes (if any) to the start of * the buffer */ oBufLength -= written; memmove(oBuf, oBuf + written, oBufLength); printf("Now have %d bytes left to send.\n", oBufLength); } } if (written > -1 || errno == EAGAIN) { /* No fatal errors... */ return 0; } else /* error left in errno for caller to inspect */ return -1; } </code></pre> <p>Note that there's no need to duplicate the buffer - since write() doesn't do anything in parallel with your code. If it says its written the bytes, it doesn't need your buffer any more. Hope that helps!</p>

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