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Networked applications need a live connection to communicate with the Internet or other nearby devices. Applications should know whether that connection exists before reaching out to send or retrieve data. Checking the network status lets the application communicate with users and explain why certain functions might be disabled.
Apple has and will reject applications that do not check the network status before providing download options to the user. Apple reviewers are trained to check whether you properly notify the user, especially in the case of network errors. Always verify your network status and alert the user accordingly.