Reachability is a tool to check if an instance can reach another instance

Examples:

# check if instance1 can reach instance2
$ reachability instance1 instance2

# Check if instance1 can reach instance2 on port 8123
$ reachability instance1 instance2:8123

# Check if instance1 can reach an ecs service which has a route53 entry
$ reachability instance1 service.ecs.local:8123