Using Multiple IP Addresses

Projects Networking, Protocols, and Devices
1

Hi, I have two problems that probably have the same answer,
Does anybody know if I can have an array of multiple IP addresses on an arduino?
I'm working in the marine enviroment and need to a) pick up an NTP time stamp and b) read several ethernet based sensors.

a)I can get my NTP time via satalite but it does not always give me an answer, so I want to be able to swap to another (IP address) provider and try again.

b)All the sensors are on the ethernet on the boat and have their own IP addresses I just need to be able to cycle through them with a 'for' loop that uses each IP address in turn to get the data.

At the moment each IP address is hard coded in the middle of the code which is not to bad for the three NTP addresses but is a bit much for the multiple sensors. By the way the sensors are not in a nice numerical sequence so I cant use (192,168,1,i) and step through 'i'.

2

An IP(v4) address is just a set of 4 bytes. You can hold that in an array and if you make an array of that you have a two-dimensional array:

uint8_t ntp_servers[][] = { { 10, 2, 4, 8 }, { 192, 168, 1, 48 }, { 172, 16, 34, 90 } };

for (int i = 0; i < 3; i++) {
  IPAddress ntp(ntp_servers[i]);
  ...
}