Disable firewall or, anti-virus software: Disable firewall or, any anti-virus software on your PC temporarily as they could prevent i Tunes from connecting to Apple servers.
The error usually occurs if you have used Redsn0w jailbreak tool, which adds the entry to the Hosts file so that i Tunes connects to Cydia servers instead of Apple update servers.

When an i Phone user sends a text message to a non-i Phone user like an Android phone, the message is sent through SMS, as is indicated by a green message bubble.
Sending text messages by SMS is also the fallback when an i Message doesn’t send for whatever reason.
There is no official solution released by Apple on its community, but we have got the answer to the problem.
So if you want to fix Invalid Address Error on your i Phone or i Pad, follow this tutorial.
Connectivity issue: On rare occasions a connectivity issue with the update server could be the reason i Tunes Error 3194 crops up.
According to Apple’s website, third party security software often prevents i Tunes from connecting to Apple servers or your i Devices. Please see the following articles to troubleshoot these errors.
You are then prompted to enter your Apple ID password to complete the installation.
If you know your password, just enter it to unlock your i Device–that’s it.
First thing first, with i OS 10.3, Apple introduces a brand new file system.