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    <p>You need to pay attention to the <a href="http://en.wikipedia.org/wiki/Endianness" rel="nofollow">endianness</a> of your architecture, particularly since the behaviour of <a href="http://msdn.microsoft.com/en-us/library/system.bitconverter.aspx" rel="nofollow"><code>BitConverter</code></a> is architecture-dependant. As it stands, your code probably fails when you are transmitting data between architectures of different endianness. Imagine, for example, a message whose size is 241 bytes. The sender – who we shall assume to be big-endian – would indicate this size by sending a byte sequence of <code>[0,0,0,241]</code>. This will be correctly interpreted as 241 on a big-endian receiver, but as 4,043,309,056 (equal to 241×256<sup>3</sup>) on a little-endian one. If you try to allocate a byte array that large, you would most likely get an <code>OutOfMemoryException</code>.</p> <p>Assuming that your incoming stream is always big-endian, you handle this by adapting your code to reverse the array when your architecture is little-endian:</p> <pre><code>buffer = new byte[4]; readBytes = ns.Read(buffer, 0, 4); if (readBytes == 0) return null; if (BitConverter.IsLittleEndian) Array.Reverse(buffer); </code></pre> <p><strong>Edit</strong>: Replying to comment:</p> <p>You need to correct for endianness whenever you’re going to use the <code>BitConverter.ToInt32</code> method to convert a 4-byte sequence into an integer. You don’t need to correct for endianness when using the <code>BinaryFormatter</code>, since it handles endianness transparently.</p> <p>I assume that endianness depends on your machine’s physical architecture, but I’ve never studied the specifics. To be safe, you should never assume a particular endianness, irrespective of whether you’re running on x86 or x64.</p> <p>If you’re responsible for the server code as well, you also need to correct for endianness there. For example, to send the <code>cmdID</code> value from the server:</p> <pre><code>int cmdID = 22; // for the example byte[] buffer = BitConverter.GetBytes(cmdID); if (BitConverter.IsLittleEndian) Array.Reverse(buffer); ns.Write(buffer, 0, 4); </code></pre>
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    1. COThanks! I added some info on end of question. So would it still appear adding this to conditional conversion as you suggest, after all my ns.Read's should be sufficient? And for my understanding, would this exception be due to the operating system architecture, or the software build? I mean, if I run the client on x64 pc, could endian-issue still occur? (without your fix I mean)
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    2. COWhile that's a flaw in his code, I don't think it's responsible for the OP's problem. Both x86 and AMD64 are little endian.
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    3. CO`BinaryFormatter` is an entirely different beast. Did you mix it up with `BinaryReader`? Sending something over the network with `BinaryFormatter` sounds like a *bad* idea.
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