[fpc-pascal] Prorammatically sending file using HTTP POST?

Wed Apr 4 13:50:25 CEST 2018

I have written a Lazarus/FPC program to configure an IoT device via a
tcp server I have implemented on the device. It all works well for
setting the parameters etc.
Now I want to also add a firmware update function to this configurator
program, but I could use some advice regarding the way to send the
file data...

The firmware updater service is running on the IoT device on port 80
as a web server and when one connects to that URL with a browser the
following happens:

1) A login dialog is shown where a username and a password needs to be
entered.

2) Next a very simple web form is shown with the following source:
<html>
<body>
<form method='POST' action='' enctype='multipart/form-data'>
   <input type='file' name='update'>
   <input type='submit' value='Update'>
</form>
</body>
</html>

3) When the "Browse..." button is clicked one gets to navigate the
file system and select a file to upload. The name is then displayed in
a box.

4) Upon hitting the submit button "Update" the file is sent to the IoT
device and used to update the firmware.

Now I want to get rid of the web browser step and integrate the
functionality of the form into the configuration program, but I don't
know how to actually send the POST data to the IoT device so it will
work...

The instructions for the WebUpdater service I have added to the IoT
device has a second alternative for uploading the firmware using curl:

curl -u user:pwd -F "image=@firmware.bin" <ip-address>:80/firmware

I don't want to require that curl is present on the PC where my
program will run, though, so I want to implement the actual post
message in my fpc code.

Does someone have a suggestion on how to do this?

By the way, I am using the Indy10 components via the indylaz package.
Lazarus is 1.8.0 and FPC 3.0.4 on Windows7.

-- 
Bo Berglund
Developer in Sweden