Hello,
I know that I can use an Ethernet Shield and connect a ethernet cable, but it is really far.. like 500 m far from the router... It is not feasible. 
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The project is working in a loop all the time and works according the information received by the sensors. How can I introduce in the code, a command like: Every time I press a button (or turn on a digital pin XXX) arduino pauses the loop, makes what I want and then continues the loop where it was paused.. Is this possible?
Sure, can do.
How? let me explain the code I have at this moment.
From 5h to 5h, Arduino turns on 4 sensors and reads the information, then according that info there is a solenoid valve that turns on if the values of the sensors are below a threshold value. This is running continuosly. I would like to have an external button (or in the future, a remote button in Cayenne App) that would turn on the solenoid valve all the times I press the button.
Best Regards,
Daniel