Why does string a return 'C' instead of "C:\Users\Desktop\Project phoneedge\ForMark\Top"?

When I tested it in a empty c project, and before I moved some of my code from ThreadFunction to StartButton it worked(The UI is suppose to update constantly but the socket recv() is cockblocking it causing it only update once so I moved the UI code to startbutton)

This is the server code, after start button is pressed, initiate the socket and there is a thread created to run the listen() accept() and recv(). The close button closes the socket and the thread.

Server Code(MFC project)

void CUIServerDlg::StartButton()
{
    WSADATA Winsockdata;
    int iTCPClientAdd = sizeof(TCPClientAdd);
    WSAStartup(MAKEWORD(2, 2), &Winsockdata);

    TCPServerAdd.sin_family = AF_INET;
    TCPServerAdd.sin_addr.s_addr = inet_addr("127.0.0.1");
    TCPServerAdd.sin_port = htons(8000);

    TCPServersocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    bind(TCPServersocket, (SOCKADDR*)&TCPServerAdd, sizeof(TCPServerAdd));

    bRunning = true;
    hthread = CreateThread(NULL, 0, ThreadFunction, this, 0, &ThreadID);
    WaitForSingleObject(hthread, INFINITE);

    funRunning = true;
    while (funRunning == true) {
        vector<string> caseOne;
    

        /*string a;
        char RecvBuffer[512];//this is the declaration in member class
        int iRecvBuffer = strlen(RecvBuffer)   1;*/

        **a = RecvBuffer;**//a is a String, RecvBuffer is a path name like c:\user..
        //Find files,This part of code is left out because it should not effect the question
        //put the files found in a vector, then display it on a listbox
        for (string fileVec : caseOne) {

            CString fileunderPath;
            string filevector1 = fileVec;
            fileunderPath = filevector1.c_str();//conversion for AddString
            list1.AddString(fileunderPath);
        }
        
        Sleep(1000);//The code updates every 1 second , when file names are modified is displays immediately.
    }    
}

I am suppose to change Sleep(1000) into WaitForSingleObject() to replace WM_Timer for the assignment but I don't know how since you need a handle, do I create another thread?

void CUIServerDlg::CloseButton()
{
    bRunning = false;
    funRunning = false;

    WaitForSingleObject(hthread, INFINITE);
    CloseHandle(hthread);
    closesocket(TCPServersocket);
}

So I have never learned anything about socket and thread prior to this project, the idea of the code below is to use a thread to run a while loop to constantly check for new cilents to send things in, do make sure to correct me if the thought process is wrong.

DWORD WINAPI CUIServerDlg::ThreadFunction(LPVOID lpParam) {

    CUIServerDlg* This = (CUIServerDlg*)lpParam;
    while (This->bRunning == true) {

        int iListen = listen(This->TCPServersocket, 10);
        if (iListen == INVALID_SOCKET)
            OutputDebugString(_T("FAIL LISTEN\n"));

        This->sAccecpSocket = accept(This->TCPServersocket, (SOCKADDR*)&This->iTCPClientAdd, &This->iTCPClientAdd);
        recv(This->sAccecpSocket, This->RecvBuffer, This->iRecvBuffer, 0);
    }

    return 0;
}

Client Code (Empty c project)

int main(){
    string a = "C:\\Users\\Desktop\\Project phoneedge\\ForMark\\Top";
    const char* SenderBuffer = a.c_str();
    int iSenderBuffer = strlen(SenderBuffer)   1;

    WSAStartup(MAKEWORD(2, 2), &WinSockData);
    TCPClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    TCPServerAdd.sin_family = AF_INET;
    TCPServerAdd.sin_addr.s_addr = inet_addr("127.0.0.1");
    TCPServerAdd.sin_port = htons(8000);

    connect(TCPClientSocket,(SOCKADDR*)&TCPServerAdd,sizeof(TCPServerAdd));

    send(TCPClientSocket, SenderBuffer, iSenderBuffer, 0);
    closesocket(TCPClientSocket);

    WSACleanup();
    system("PAUSE");
    return 0;
}

CodePudding user response：

The TCP protocol passes the data by byte stream.

It means the client passes the data byte by byte rather than pass all the data at one time.

When you receive the data from the client. The passing procedure maybe not be finished.

So you need to check whether the data is finished passing after receiving some data by one recv call and then save the sub-data until receiving all the data.