4 Raspberry pi gateway

Gateway to operate as a collector and the main link between many controllers and the cloud application as follows: 1. authentication should be done between the gateway and the cloud and between the controllers with the gateway to maintain a secure communication. 2. The communication Protocol between the cloud and gateway and all controllers must be MQTT Protocol. 3. the gateway will just receive the instructions from the cloud to any Controller, then it will send it to that controller to execute the instructions and also receive the data from all controllers to sent them to the cloud in the following format : ( controller no., PIN number, instruction, time duration). 4. The raspberry pi will be connected to some sensors (LDR,PIR, temp., Counter and relays) for some certain instructions that will be received from the cloud through MQTT Protocol and the raspberry pi should just execute it as it is without any processing. Ex(PIN A.1, ON, for 3 hours). if you are aware of such requirements and willing to do it at the PRICE You OFFERED please quote. Taking into consideration that the max. Budget is 75$ and only serious and committed freelancer please because increasing the price for such scope of work after submitting your price is not acceptable. Best regards