10038 wsa socket error recv

Question

I'm currently trying to implement a class to create and use TCP connections. (I'm quite new in c++ so it's possible that I forgot something obvious, even though I've been seriously checking my code)

Note that later I'll be implementing a second class to handle new connections so there are some parts of the code that are incomplete/arranged and I hope that this won't disturb you while trying to understand it.

Here's my problem:

The server and the client both seem to work fine (I'm always checking on my listen, bind, connect functions: no error) and I'm apparently able to send data with the client but when I try to read it from the server, I get WSA error 10038 (which means that i'm executing the recv() on an invalid socket). I've been looking it up for a few days now and can't seem to find my mistake. Besides the tests in the code, I've used "netstat -an -p tcp" to check the state of the connection and everything appears fine but the server just won't receive the data.

NB: I'm using Visual Studio 6 (Yup, it's old, but it's mandatory so...) and winsock, not winsock2.

If I forgot something just ask, i'm trying to be as complete as possible but it's not impossible to forget something.

Here are my source codes, i tried to cut it to the essential but i'm afraid that the mistake can be pretty much anywhere:

CmTcpTransport.cpp

/**
Initializes the TCP connexion (socket) in CLIENT or SERVER mode.
It does not connect yet.

@param strIPAddress: IP Adress to reach
       nPort: Port to connect to
       hSocket: client Socket if SERVER mode
       nTcpMode: mode for this connexion SERVER(1) or CLIENT(2)      

@return an int to get the exit point of the function
*/
int CmTcpTransport::initialize(std::string strIPAddress, unsigned int nPort,         SOCKET hSocket, int nTcpMode)
{
m_nTcpMode = nTcpMode; 

cout << "Creating TCP connexion..." << endl << endl;

if (nTcpMode == 1) // SERVER
{

    serveraddr.sin_family = AF_INET; // address family Internet
    serveraddr.sin_port = htons (nPort); // Port to connect on
    serveraddr.sin_addr.s_addr = inet_addr (strIPAddress.c_str()); // Target IP

    cout << "SERVER: Retreaving socket information..." << endl; 

    if (hSocket == INVALID_SOCKET)
    {
        return 102; // The received socket is invalid
        cout << "SERVER: Socket creation failed" << endl;
    }  

    serverSocket = hSocket;

    cout << "SERVER: Listening socket received" << endl;

    if (bind(serverSocket, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) == SOCKET_ERROR)
    {
        return 103; // Couldn't bind
        cout << "SERVER: Socket binding failed" << endl;
    }   
    else {
        cout << "SERVER: Binding successful" << endl;
    }

    if (listen(serverSocket, 1) == SOCKET_ERROR)
    {
        return 103; // Couldn't listen
        cout << "SERVER: Socket listening failed" << endl;
    }
    else {
        cout << "SERVER: Listening to socket" << endl;
    }

}
else // CLIENT
{
    serveraddr.sin_family = AF_INET; // address family Internet
    serveraddr.sin_port = htons (nPort); // Port to connect on
    serveraddr.sin_addr.s_addr = inet_addr (strIPAddress.c_str()); // Target IP

    cout << "CLIENT: Creating client socket..." << endl;

    clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); // CREATE CLIENT SOCKET

    if (clientSocket == INVALID_SOCKET)
    {
        return 104; // Couldn't create the socket
        cout << "CLIENT: Socket creation failed" << endl;
    }  

    cout << "CLIENT: Client socket created" << endl;


}

cout << "Initialization succeeded." << endl << endl << endl;
return 105;
}

/**
Creates the connexion to TCP

@param none        
@return an int to get the exit point of the function
*/
int CmTcpTransport::connectTcp()
{


if (m_nTcpMode == 1) // SERVER
{
    cout << "Waiting for connexion..." << endl;
    int clientLen(0);
    clientLen = sizeof(clientaddr);


    if ((clientSocket = accept(serverSocket, (SOCKADDR *)&clientaddr, &clientLen) == INVALID_SOCKET))
    {
        cout << "SERVER: Connexion failed." << endl;
        return 202;; // Couldn't listen
    }
    else {
        cout << "SERVER: Connexion established." << endl << endl << endl;
        if (clientSocket == SOCKET_ERROR) 
        {
            printf("socket became invalid after connexion:: %d\n", WSAGetLastError());
        }
        else {
                cout << "SOCKET STILL VALID AND WORKING AFTER CONNEXION" << endl;
        }
        return 201;
    }


}
else // CLIENT
{
    cout << "Connecting..." << endl;
    if (connect(clientSocket, (SOCKADDR *)&serveraddr, sizeof(serveraddr)) == SOCKET_ERROR)
    {
        cout << "CLIENT: Connexion failed." << endl << endl << endl;
        return 202;; // Couldn't connect
    }
    else 
    {
        cout << "CLIENT: Connexion to server succeeded." << endl << endl <<         endl;
    }
    return 203;
}
}

/**
Receives a buffer of bytes from the TCP

@param buffer: buffer to store the data
       bufLen: size of the buffer

@return nbChar: the result of the recv function
if no error occurs, recv returns the number of bytes received
else, it returns a value of SOCKET_ERROR
*/
int CmTcpTransport::recvTcp(char *buffer, int bufLen)
{
if (clientSocket == SOCKET_ERROR) 
        {
            printf("socket became invalid before receive:: %d\n",  WSAGetLastError());
        }
        else {
                cout << "SOCKET STILL VALID AND WORKING BEFORE RECEIVE" <<         endl;
        }

int nbChar = recv(clientSocket, buffer, bufLen, 0);
if (nbChar == SOCKET_ERROR)
{
    printf("recv failed: %d\n", WSAGetLastError());
    cout << "No data received." << endl << endl << endl;
    return nbChar;
}
else {
    buffer[nbChar]=0; // Gestion de la taille du buffer
    cout << "Data received: " << buffer << endl << endl << endl;
    return nbChar;
}
}
/**
Sends a buffer of bytes to the TCP

@param buffer: buffer containing the data
       bufLen: size of the buffer

@return nbChar: the result of the send function
if no error occurs, recv returns the number of bytes sent
else, it returns a value of SOCKET_ERROR
*/
int CmTcpTransport::sendTcp(char *buffer, int bufLen)
{

int nbChar = send(clientSocket, buffer, bufLen,0);
if (nbChar == SOCKET_ERROR)
{

    cout << "No data sent." << endl << endl << endl;
    return nbChar;
}
else {
    cout << "Data sent: " << buffer << endl << endl << endl;
    return nbChar;
}
}

server main.cpp

int main(int argc, char* argv[])
{
// ----------------------- WINSOCK ----------------------------

cout << "Initializing winsock library..." << endl;

// Start up Winsock
WSADATA wsadata;

int error = WSAStartup(0x101, &wsadata);

// Error ?
if (error) 0;

// Try Winsock Version ?
if (wsadata.wVersion != 0x101)
{
    WSACleanup(); // Clean up Winsock
    return 101;
}

cout << "Initialization successful" << endl << endl << endl;


// ----------------------- SERVER ---------------------------

char buffer[3000];

int testRecv; // return of the recv function

cout << "SERVER" << endl << endl << endl;

// Simulate the activity of the TcpListener transfering a listening Socket for the client connexion
SOCKET testSocket;
testSocket = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP); 

// Creating a new TCP transport
CmTcpTransport server;

// Initialize and connect the TCP transport
server.initialize("127.0.0.1", 10000, testSocket, TTCP_MODE_SERVER);

server.connectTcp();

// Try to receive data
testRecv = server.recvTcp(buffer, sizeof(buffer));

cout << testRecv << endl;

// Disconnect
server.disconnectTcp();


return 0;
}

client main.cpp

int main(int argc, char* argv[])
{

// ----------------------- WINSOCK ----------------------------

cout << "Initializing winsock library..." << endl;

// Start up Winsock
WSADATA wsadata;

int error = WSAStartup(0x0202, &wsadata);

// Error ?
if (error) 0;

// Try Winsock Version ?
if (wsadata.wVersion != 0x0202)
{
    WSACleanup(); // Clean up Winsock
    return 101;
}

cout << "Initialization successful" << endl << endl << endl;


// ----------------------- CLIENT ---------------------------

char buffer[10000];

cout << "CLIENT" << endl << endl << endl;

// this Socket won't be used as the TCP transport is in client mode
SOCKET test;
test = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP);

// Create, initialize and connect the client TCP transport
CmTcpTransport client;

client.initialize("127.0.0.1", 10000, test, TTCP_MODE_CLIENT);

client.connectTcp();

// Copy the data in the buffer and send it
strcpy(buffer, "Test donnees");

client.sendTcp(buffer, sizeof(buffer));

client.disconnectTcp();

return 0;
}

And here are screenshots of my consoles when I run both mains:

http://www.hostingpics.net/viewer.php?id=892752Consoles.jpg

Thank you for your help, I realize this is a lot to read/process and I appreciate the effort !

Answer 1

I think you are invalidating the new sock-id on accept with incorrect braces :

if ((clientSocket = accept(serverSocket, (SOCKADDR *)&clientaddr, &clientLen) == INVALID_SOCKET))

Try changing it to :

if ((clientSocket = accept(serverSocket, (SOCKADDR *)&clientaddr, &clientLen)) == INVALID_SOCKET)