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    <p>This is a very bad idea. Binary data should always be sent in a way that:</p> <ul> <li>Handles different <a href="http://en.wikipedia.org/wiki/Endianness" rel="noreferrer">endianness</a></li> <li>Handles different <a href="http://en.wikipedia.org/wiki/Data_structure_alignment#Data_Structure_Padding" rel="noreferrer">padding</a></li> <li>Handles differences in the <a href="https://en.wikipedia.org/wiki/Word_(computer_architecture)#Table_of_word_sizes" rel="noreferrer">byte-sizes of intrinsic types</a></li> </ul> <p>Don't ever write a whole struct in a binary way, not to a file, not to a socket.</p> <p>Always write each field separately, and read them the same way.</p> <p>You need to have functions like</p> <pre><code>unsigned char * serialize_int(unsigned char *buffer, int value) { /* Write big-endian int value into buffer; assumes 32-bit int and 8-bit char. */ buffer[0] = value &gt;&gt; 24; buffer[1] = value &gt;&gt; 16; buffer[2] = value &gt;&gt; 8; buffer[3] = value; return buffer + 4; } unsigned char * serialize_char(unsigned char *buffer, char value) { buffer[0] = value; return buffer + 1; } unsigned char * serialize_temp(unsigned char *buffer, struct temp *value) { buffer = serialize_int(buffer, value-&gt;a); buffer = serialize_char(buffer, value-&gt;b); return buffer; } unsigned char * deserialize_int(unsigned char *buffer, int *value); </code></pre> <p>Or the equivalent, there are of course several ways to set this up with regards to buffer management and so on. Then you need to do the higher-level functions that serialize/deserialize entire structs.</p> <p>This assumes serializing is done to/from buffers, which means the serialization doesn't need to know if the final destination is a file or a socket. It also means you pay some memory overhead, but it's generally a good design for performance reasons (you don't want to do a write() of each value to the socket).</p> <p>Once you have the above, here's how you could serialize and transmit a structure instance:</p> <pre><code>int send_temp(int socket, const struct sockaddr *dest, socklen_t dlen, const struct temp *temp) { unsigned char buffer[32], *ptr; ptr = serialize_temp(buffer, temp); return sendto(socket, buffer, ptr - buffer, 0, dest, dlen) == ptr - buffer; } </code></pre> <p>A few points to note about the above:</p> <ul> <li>The struct to send is first serialized, field by field, into <code>buffer</code>.</li> <li>The serialization routine returns a pointer to the next free byte in the buffer, which we use to compute how many bytes it serialized to</li> <li>Obviously my example serialization routines don't protect against buffer overflow.</li> <li>Return value is 1 if the <code>sendto()</code> call succeeded, else it will be 0.</li> </ul>
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    1. POPassing a structure through Sockets in C
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    1. COAnd in this case, `int` can have different sizes on the different machines as well.
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    2. CO@Douglas: Absolutely true, and added the list. Thanks!
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    3. CO@unwind - Are serialize_int and deserialize_int are standard functions ??
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