Checking for the Internet before accessing the Internet data is the right way to do in any app that you make in any platform.

Here is a small gist to make the network check on Corona SDK. Either use the code in the same Lua file you use or use a separate utility lua file to add the functions. Check here for making the Utility file in Corona SDK (Lua).

local iosNetworkAvailable = true -- 1

function networkListener( event )
    iosNetworkAvailable = event.isReachable
end

if ( network.canDetectNetworkStatusChanges ) then
    network.setStatusListener( "www.apple.com",networkListener ) -- 2
end

function isRechable()
  local os = system.getInfo("platformName")
  if ( os == "iPhone OS") then
      return iosNetworkAvailable -- 3
  elseif ( os == "Android" ) then
    local socket = require("socket") -- 4
    local test = socket.tcp()
    local isNetworkAvailable = false
    test:settimeout(3000) -- Set timeout to 3 seconds
    local testResult = test:connect("www.google.com",80) -- Note that the test does not work if we put http:// in front 
    if not(testResult == nil) then -- 5
      print("Internet access is available")
      isNetworkAvailable = true 
    else
      print("Internet access is not available")
      isNetworkAvailable = false
    end
    test:close() -- 6
    test = nil
    return isNetworkAvailable -- 7
  end
end

Usage :

In the function where you want to check for the utility, just call the function, which will return you the network status.

if isRechable() == true then 
  -- Network is Available Here. Do Something
else 
  -- Network is Not Available Here.
  native.showAlert( "No Internet","It seems internet is not Available. Please connect to internet.", { "OK" } )
end

Code Explanation :

1 — create a local variable.

2 — Create a network listener function available in the network library. Note that this will work only on iOS, so we are using sockets for Android.

3 — we are checking for the Platform and if its iOS, we are sending the status using the network listener which automatically changes the value of the isNetworkAvailable variable.

4 — Using the Sockets to check the internet connection if the platform is Android.

5 — Based on the Socket test result, we are setting the value for the isNetworkAvailable variable.

6 — Close the test connection

7 — return the isNetworkAvailable Variable.

That's for the Network. Happy coding!