Several users have noted recurrence of a relatively longstanding issue in which iTunes suddenly stops connecting to the iTunes store. When users try to enter the store they may receive a "network connection timed out error".
Apple Discussions poster ruffstuff writes:
"I keep on getting this error now "We Could Not Complete your iTunes Store Request. The Network Connection Timed Out". What is depressing is that about 24 hours ago, i was still able to download a video from the iTunes store? Now I can't even sign into the iTunes Store."
The iTunes store uses standard web port numbers and protocols for network communications, which makes accessing the store essentially like viewing a web page. As such, if the web is working, the iTunes store should work. However, users experiencing this issue are otherwise access the internet and do other network-based activity, only receiving a timed-out error when accessing the store. Users have tried targeting the application itself by removing various preferences as well as repairing permissions on the boot drive, but this has not resolved the issue.
This problem has affected both Mac and Windows users, and indicates that there is a problem with the user's firewall or router connections, because the problem seems to suddenly appear and not be caused after any updating or program modification. In support of this postulation, one user took his Mac Mini to another location and was able to connect properly, which indicates the problem is either in the broadband router or in the ISP's account settings.
Additionally, one user replaced his home router and the problem went away. As such, users (especially laptop owners) are encouraged to try their iTunes connections through different broadband accounts and setups.
While replacing the router and other network hardware seems to fix the problem for some users, there are several things users can try before spending money on a new router. For some of these fixes, users will have to edit the settings on their routers, and should consult their user manual for exact instructions.
Wait it out For some users, the problem seems to suddenly disappear just as fast as it arrived. This indicates the problem can be overcome, but it also indicates potential conflicts between iTunes and the router software which could crop up again in the future.
Setup DMZ for the affected computer Routers contain firewalls and other network technology that may be causing this problem, but most also have support for a "Demilitarized Zone" (DMZ) computer which is not put behind the firewall. This is a convenient way to test the router, and users should first find what IP address is being given to their computer, and then set that IP address as the DMZ computer. If iTunes connectivity works, then the problem is clearly with the firewall settings in the router.
Ensure ports 80 and 443 are open The router should have internet ports 80 (http) and 443 (https) open by default, but it is possible some setting has changed to restrict these ports in some situations, possibly by them being reserved for a specific IP address on the network through port forwarding. These settings can be automatically set in some cases, so users should check and remove any port forwarding or port triggering settings that might include these numbers.
Disable Firewalls Routers usually contain some sort of firewall which is enabled by default. As a test, users might try disabling the various firewalls that are on the router. These might include NAT, SPI, or content filters, in addition to "true" firewalls which block specific ports and services. If any options to disable firewalls are available in the router's settings, users are encouraged to try turning them off.
Toggle UPnP settings Most modern routers support a network technology called Universal Plug and Play (UPnP) which automatically assigns ports and other network settings to computers behind routers in an "on-demand" fashion, which helps reduce the amount of configuration that needs to be done. Users might try connections with UPnP both enabled and disabled.
Update Router Firmware If various settings do not work, users might ensure their router's firmware is up to date. Many have an automatic-update feature, but most require a user to download a file from the manufacturer's support site and then upload it to the router. If this does not fix the problem then users may have to replace their routers. Unfortunately there seems to be a trend that this problem revolves around several Linksys Wireless router models, and it could be an bug in the firmware of these models that's causing the problem.