QTCPSocket - Download Speed

[tntcoda]

Hi,

I'm wondering if someone could kindly help me with a high level design for how to download through a QTCPSocket, in order to obtain reliable downstream speeds in real time.

Its a custom protocol, but basically once I issue a request for some data, I need to keep downloading until I receive the terminating bytes <CR><LF>.<CR><LF>

Here is my current thinking:

- Request data download
- Record current timestamp
- Read X bytes through the socket
- Record new timestamp, compute time difference and work out speed for the transfer of X bytes, signal this out...
- Repeat until terminating bytes: <CR><LF>.<CR><LF> are detected.

Does this seem like a solid approach to the problem? If so, my question is how many bytes should I read per cycle (size of X)?

Baring in mind the transfer size could be a few bytes to many megabytes, what transfer cycle size is good for best performance, and also enough to calculate reliable, real-time download speeds?

I guess also I would need to record the last cycles data in case half of the terminating bytes came through at the end of the last cycle?

Many thanks for any help,

Jack

[wysota]

You should recalculate the speed each time you receive new data to provide better and better approximation of the average speed. How to approximate is up to you - you can either use the whole download history or only the recent part (i.e. last 10s of download). To store the statistics you can use a simple QMap<QTime,int> to store amounts of data downloaded during subsequent periods of time.

[tntcoda]

Thanks that makes sense, will go down that route.