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POsocket connect() returning 0 even after peer reset
 

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    <p>I have an iPad app in which I'm creating and connecting a posix <code>socket</code>. Calls to <code>connect(...)</code> are not responding as expected when the remote device rejects the connection attempt.</p> <p>A simplified example of how I'm creating and connecting the <code>socket</code>:</p> <pre><code>struct sockaddr_in server; server.sin_family = AF_INET; int socket = socket(AF_INET, SOCK_STREAM, 0); if(socket &lt; 0) { NSLog(@"socket create failed: %s", strerror(errno)); } else if(inet_aton(mAddress, &amp;server.sin_addr)) { server.sin_port = htons(mPortNumber); if(connect(socket, (struct sockaddr *)&amp;server, sizeof(server)) == -1) { NSLog(@"connect() failed: %s", strerror(errno)); } else { NSLog(@"connect() succeeded"); } } </code></pre> <p>In most cases, the above example works: e.g. for a remote device (hereafter referred to as 'the server') which is accepting connections, <code>connect()</code> returns <code>0</code> as expected. For a non-existent address, <code>connect()</code> blocks for a while then returns <code>-1</code>, and <code>errno</code> is <code>ETIMEDOUT</code>.</p> <p>From the docs, if the server rejects the connection attempt I would expect <code>connect()</code> to return <code>-1</code> and for <code>errno</code> to be <code>ECONNREFUSED</code> or perhaps <code>ECONNRESET</code>. Instead, <code>connect()</code> returns <code>0</code>.</p> <p>I've WireSharked the TCP conversation multiple times and can confirm that only ever consists of two packets:</p> <blockquote> <p>Client (iPad) -> Server: <code>SYN, ACK</code></p> <p>Server -> Client (iPad) : <code>RST, ACK</code></p> </blockquote> <p><strong>Why does connect return <code>0</code>?</strong></p> <p>Update: Connecting to the same server from a different client, e.g. Qt on Windows (winsock?) or Mac OSX (also posix) works as expected: i.e <code>connect()</code> returns <code>-1</code>, <code>ECONNREFUSED</code>. This leads me to believe it's a problem with the iPad end rather than the server end.</p>
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    1. CO"*... if the remote device rejects the connection attempt ...*" I'm not sure if `to reject` is a well defined action interms of tcp/ip connection setup, so you might like to elaborate on how you define it.
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    2. COWhat I mean by a 'refused connection' is one with a TCP conversation like the one above, i.e. the client tries to `SYN` and the server replies with a `RST`. What terminology would you use to describe this?
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    3. CONo `SYN-ACK` from the Remote in repsonse to the iPad's SYN?
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