I'm using the qextserialport classes in Qt to implement serial transmissions between devices. Now, I'm required to send a file between devices connected via USB using the serialport. I have used the serialport for various functions in the past weeks but I have no idea where to start implementing this. I thought about reading data event-driven until there is no more data to read, determine the size (number of bytes) of the file before hand and send it together with the data so that it would be clear if data went missing. I also have a correct function that calculates the CCIITT 16 bit checksum so I can use that for checking as well. My question therefore is:
Can someone please send me a link to a site that could help solve my problem and explain to me what would be the most simple and effective way to send a file and receive a file via the qextserialport class in Qt. ANY help would be awsum!
You need a protocol. Simple one could be:
send length of file name as raw binary number, for example 2 bytes in network byte order (max name length 65535 bytes)
send that many bytes of file name, encoded with UTF-8
send file size as raw binary number, for example 4 bytes in network byte order (max file size 4 gigs)
send that many bytes of file contents
You might want to add info like file date, and checksum. More advanced would be to split file to chunks, so if there is transmission error, you don't have to re-send everything. Etc.
Also, study protocols like Kermit, xmodem, zmodem to see how it's been done in the modem and BBS era. Maybe use an existing protocol like that instead of creating your own.
Note: while you could use
QDataStream, it requires reliable channel, so it's not as easy as it may seem at first (requires extra buffering).