@alinanco @Hootie81 Some cores can catch a problem where they no longer can do DNS lookups. The TCPClient connect method can either accept a char * or a IPAddress. Any char * passed will result in a call to gethostbyname that fails once the core gets into this bad state. You should try creating the IPAddress as @Hootie81 recommends and pass that IPAddress to the TCPClient.connect call.
If you absolutely need DNS lookup capabilities then there is a library you can add to your application that you can use for DNS lookups and then pass the IPAddress to the TCP calls.
I have noticed not all Spark Cores have this problem. I have 5 cores and one has this problem.