Thread: char problem

after long searching i finally found the function that gets the data size of the main casyncsocket buffer atleast i think so

Code:

if(nErrorCode==0)
    {
        DWORD rcv;
        CString Data;
        wsClient.IOCtl(FIONREAD,&rcv);
        char *dta=new char[rcv-1];
        wsClient.Receive(dta,rcv,0);
        dta[rcv]='\0';
        Data=dta;
        delete[]dta;
        CString txt;
        m_re1.GetWindowText(txt);
        m_re1.SetWindowText(txt+CString("\n")+Data);
    }

FIONREAD Determines the maximum number of bytes that can be read with one Receive call from this socket. The lpArgument parameter points at a DWORD in which IOCtl stores the result. If this socket is of type SOCK_STREAM, FIONREAD returns the total amount of data which can be read in a single Receive; this is normally the same as the total amount of data queued on the socket. If this socket is of type SOCK_DGRAM, FIONREAD returns the size of the first datagram queued on the socket.

i guess thats what i need right ?

btw how do i messagebox a dword value so i can see if that function really works for sure

>>If this socket is of type SOCK_STREAM, FIONREAD returns the total amount of data which can be read in a single Receive;

the max amount that can be read in one recv is the size of the sockets recv buffer. This amount can be changed with SetSockOpt() as I stated.

This will not solve your problem as you can NOT be sure all data will be recv'ed in one read even if sent in one write.


>>do i messagebox a dword value so i can see if that function really works for sure

CString Format(). Look at sprintf() and follow to 'type specifiers'.

"printf Type Field Characters" in MSDN's Run-Time Library Reference.

a DWORD is a 32 bit unsigned int (try %u)

Originally Posted by novacain

This will not solve your problem as you can NOT be sure all data will be recv'ed in one read even if sent in one write.

why not ? this is exactly what i needed i made some tests and it works perfectly the ammount of memory declared in the buffer is the same as the casyncsocket buffer size, since its in the queue in the buffer it should be received all with no problem
If this socket is of type SOCK_STREAM, FIONREAD returns the total amount of data which can be read in a single Receive; this is normally the same as the total amount of data queued on the socket.
oh btw i got that code working, showing a dword value and i gotta tell you that i saw the exact number of the chars that were received in the chat
thanks for replying

NOTE: You probably won't see this with a chat app as the data sent is small. It could happen, especially if an error (ie lost packet) occurs. If you app does not handle it then the results are usually terminal.



After you write to the socket TCP/IP takes over. It breaks the data up into packets, adds error checking and sends the data.

On your client end the data is re-assembled, any damaged or lost packets are re-requested.

At this point the socket does not 'wait' until the message you 'sent' arrives, any amount of data can be recv'ed.

The message could arrive in multiple recv's or multiple msg's could arrive togather (one after another, all in one recv) .

Try getting your server to send data close to the recv buffer size multiple times and see if an error occurs.