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POWinsock2 tcp/ip - some data packets are ignored probably due to null terminator from the previous packet
 

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  1. POWinsock2 tcp/ip - some data packets are ignored probably due to null terminator from the previous packet
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    <p>I wrote a simple client-server program. Network.h is a header file which uses Winsock2.h (TCP/IP mode) to create socket, accept/connect in blocking mode, send/recv in non-blocking mode. I made it so that the function <code>string TNetwork::Recv(int size)</code> will return the string "Nothing" if it gets WSAWOULDBLOCK error (no data is received yet)</p> <p>Here is my main function:</p> <pre><code>int main(){ string Ans; TNetwork::StartUp(); //WSA start up, etc cin &gt;&gt; Ans; if (Ans == "0"){ // 0 --&gt; server TNetwork::SetupAsServer(); //accept connection (in blocking mode!) while (true){ TNetwork::Send("\nAss" + '\0'); //without null terminator, the client may read extra bytes, causing undefined behavior (?) TNetwork::Send("embly" + '\0'); cin &gt;&gt; Ans; } } else{ // others --&gt; regard Ans as IP address. e.g. I can type "127.0.0.1" TNetwork::SetupAsClient(Ans); string Rec; while (true){ Rec = TNetwork::Recv(1000); if (Rec != "Nothing"){ cout &lt;&lt; Rec; } } } system("PAUSE"); } </code></pre> <p>Supposedly, the client would print "Assembly" when connected, and when the server enters anything to its console window. Sometimes, though, the client would only print out "\nAss" in the console without the "embly.</p> <p>To my understanding, TCP/IP ensures all data to be sent and in the correct order, so I guess what happens is that both packets arrive at the same time, which happen quite often over the unstable internet. And due to this null terminator, the client would ignore the "embly", since the Recv() function stopped reading when it hits a null terminator.</p> <p>So, how can I ensure that the client will always read all data packets correctly?</p>
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    1. USVincentius Kevin
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    1. COIf there is a solution to send packets without the null terminator, somehow, I won't mind as well. I would change any part of the code if it works. I'm relatively new to winsock2 (as well as socket programming) so I probably have some basic mistakes.
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      1. USVincentius Kevin
    2. CONull termination and TCP have nothing to do with each other. You're barking up the wrong tree here. The TCP send and receive APIs take pointer and length arguments and they place no interpretation on the contents whatsoever.
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      1. USuser207421
 

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