Connect and send on the socket succeeds, even if Wi-Fi not enabled and server is only reacheable in the wireless network - Windows Mobile 6.5 - C/C++

Question

I wrote a small C/C++ Windows Mobile 6.5 client-application that is connecting to a server and sends some data to this server. The server is in my internal wireless network and is not reacheable outside.

The weird behaviour I'm having:

1. Even if the Wi-Fi is not started on my mobile device, the connect() from the client-application returns success (!= SOCKET_ERROR), which is not the case b/C the server is reacheable only in the wireless network.

2. If the Wi-Fi is not started on my mobile device, if there is a Sleep (1000) between the connect() and the send(), the send() fails with WSAECONNRESET, BUT if there is no Sleep() between the connect() and send() the send() succeeds! (Only when doing the read() I finally get the WSAECONNRESET error).

It's pretty scary that without actually being able to reach the server I still get success for the connect() and for the send()

As requested, here is a sample code:

#include <windows.h>
#include <Winsock2.h>
#include "dbgview.h"

#   define FxMemZero(buf,len)       RtlZeroMemory ((VOID*)(buf),(SIZE_T)(len))
#   define FxMemCopy(dst,src,len)   RtlCopyMemory ((VOID*)(dst),(CONST VOID*)(src),(SIZE_T)(len))


int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPTSTR    lpCmdLine,
                   int       nCmdShow)
{

    SOCKET proxy_connection;
    WSADATA wsadata;
    if( 0 != WSAStartup (MAKEWORD(1, 1), &wsadata))
        return -1;

    proxy_connection = WSASocket (AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, 0);
    if(proxy_connection == INVALID_SOCKET) {
        // error creating the socket
        DbgViewTraceError((L"main", L"error creating socket."));
        return -1;
    }
    // try to connect
    UINT proxy_ip_ = 0x00000000;
    CHAR* proxy_0_ =  "192.168.1.105";
    UINT proxy_port = 3100;
    // get the proxy ip
    {
        struct hostent *he_;
        if((he_ = gethostbyname(proxy_0_)) == NULL) {
            DbgViewTraceWarning((L"main", L"error %d resolving hostname %hs", WSAGetLastError(), proxy_0_));
            return -1;
        }
        FxMemCopy((PBYTE)&proxy_ip_, (PBYTE)he_->h_addr, he_->h_length);
    }
    // prepare the connection data
    sockaddr_in saddr_;
    FxMemZero(&saddr_,sizeof(sockaddr_in));
    saddr_.sin_family = AF_INET;
    saddr_.sin_addr.S_un.S_addr = proxy_ip_;// address
    saddr_.sin_port = htons((USHORT)proxy_port);
    // do the conection
    if(SOCKET_ERROR == connect(proxy_connection, (SOCKADDR*) &saddr_, sizeof(saddr_))) {
        // error connecting to the proxy
        DbgViewTraceWarning(( L"main", L"error %d connecting to %hs:%d", WSAGetLastError(), proxy_0_, proxy_port));
        closesocket(proxy_connection);
        proxy_connection = INVALID_SOCKET;
        return -1;
    }
    DbgViewTraceInfo(( L"main", L"SUCCESS. connected to %hs:%d.", proxy_0_, proxy_port));


    CHAR* buffer_ = "Momo";
    UINT  count_  = strlen(buffer_);
    DWORD total_  = 0;
    DWORD sent_   = 0;
    while(total_ < count_) {
        // ISSUE: IF the WIFI is not started on the mobile, the connect returns success AND the send() returns success, even though with putty
        //   on the mobile, a telnet on 192.168.1.105:3100 will fail with: "Network error: Connection reset by peer"
        //   IF I add a long-enough Sleep() between the connect() and the send(), the send() will fail with: WSAECONNRESET
        //Sleep(5000);
        if(SOCKET_ERROR == (sent_ = send(proxy_connection, (const char*)buffer_ + total_, count_ - total_, 0))) {
            // error sending data to the socket
            DbgViewTraceError((L"main", L"error %d sending data to proxy", WSAGetLastError()));
            return -1;
        }
        total_ += sent_;
    }
    DbgViewTraceInfo((L"main", L"send() SUCCESS"));
    return 0;
}

The results are:

1. Without Sleep():

main   [INFO   ]  SUCCESS. connected to 192.168.1.105:3100.

main   [INFO   ]  send() SUCCESS

2. With Sleep():

main   [INFO   ]  SUCCESS. connected to 192.168.1.105:3100.

main   [ERROR  ]  error 10054 sending data to proxy

So the questions are:

1. Why the connect() succeeds? How can I be sure that there is actually a real connection?

2. Why the send() succeeds?

3. Why with a Sleep() in between connect() and send() the behaviour is different?

---

The problem seems to be ActiveSync. If ActiveSync is running, I get the behavior described above (connect() and send() report success, even though they are not). If ActiveSync is not running, gethostbyname() fails with:

• WSAENETDOWN -> if Wi-Fi is disabled

• WSAHOST_NOT_FOUND -> if Wi-Fi is enabled

Which is correct!

How can this be? What is ActiveSync doing that is ruining everything? How can I avoid this problem? I mean, I can't be sure that the user is running my application when there is no ActiveSync running, so what can I do to avoid this behavior when ActiveSync is running?

Answer 1

Looks like you are at least misusing struct sockaddr_in. Try more modern API for address conversion - Windows has InetPton - and see if that fixes the issues.