change an HTTP protocol

an application uses HTTP to send a file to a dedicated Linux server. Inside the server, the file is processed and a new file is sent back to the application. The pseudocode is: 1. the client sends username and password 2. the server gets username and passwords and validates them against values stored in a database table 3. if username and password don't match, an 'invalid password' message is sent back to the client 4. if username and password do match, an ID is sent back to the client 5. the client sends the file to process together with the ID 6. the server processes the file and send back the processed file to the client Both client code snippets (in Delphi) and server side code (in PHP) is attached. We want to change the protocol this way: 1. idem 2. idem 3. idem 4. idem 5. idem 6. the server processes the file and writes the processed file to disk using the ID as filename 7. the client polls the server every X seconds looking for a filename of name ID 8. when the file is found, the client downloads it 9. if the file is not found inside time T, the polling is stopped and message 'no processed file found after T seconds' is returned to the user The selected coder will have skills in PHP, Linux and HTTP He will: 1. change the few required lines in the PHP code (<10 lines of code) 2. guide our Delphi coder along the changes required to the client application 3. perform the tests until ev works