Modem Connections: 3 Sending Data

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To send data, MTalk does the following:

retrieves the text the user has typed in and puts it into a memory block
locks the block down (to get a pointer to the text)
gets the size of the text
calls ModemSend() (defined in modem.goc) to send the data
unlocks the memory block

Code Display 9-2 Sending Data Over A Serial Connection

    /*
     * textBlock - Handle of block containing text to send.
     * textPtr - Pointer to text to send.
     * textSize - Size of text to send.
     */
    MemHandle		textBlock;
    char *		textPtr;
    int		textSize;

    /*
     * Get text that user has typed and put it into a newly created memory block.
     * Lock the block down on the heap and obtain a pointer to it.
     */
    textBlock = @call MTalkSendText::MSG_VIS_TEXT_GET_ALL_BLOCK( NullHandle );
    textPtr = MemLock( textBlock );

    /*
     * Get the size of the text then send it.
     */
    textSize = LocalStringSize( textPtr );
    if ( ModemSend( textSize, (byte*)textPtr ) != STREAM_NO_ERROR )
    {
	/* handle the error */
    }

    /*
     * Once the text has been sent, free its block.
     */
    MemFree( textBlock );

ModemSend() calls the VirtualSerial Library routine, VirtualSerialWrite() , to send the passed data. VirtualSerialWrite() writes the passed data to stream and, if necessary, blocks until enough space in the stream becomes available. (If you don't want to block, pass STREAM_NO_BLOCK in VirtualSerialWrite() .)

ModemSend() takes two arguments:

dataLength: Length of the string (not counting the Null character).
data: Pointer to the data to be sent.

ModemSend() returns a StreamError value:

STREAM_NO_ERROR: if it successfully sends the data.
STREAM_CLOSED: if the stream is not open.
STREAM_SHORT_READ_WRITE: if the required amount of space was not available and STREAM_NO_BLOCK was specified.

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4 Receiving Data