Is there a way to create a private wifi network, i.e. for file sharing? Consider there are 2 notebooks (Win-Win or Mac-Win or Mac-Mac) and someone wants to share some content with other. How can I create such kind of network?
Setup an ad-hoc WiFi network.
Win-Mac - Choose one of the two above options, and connect to the new network as a client on the other PC.
If the Mac-Mac case is Lion-Lion with relatively recent Macs, then just click on the AirDrop icon on the sidebar of any Finder window on each machine. Lion takes care of discovering other recent Lion Macs in wireless range and displaying them in the AirDrop window, and then you just drag files right onto their icons and Lion takes care of encrypted point-to-point high speed wireless transfer of those files.
My MacBook Pro will not automatically connect to a Wireless network with a hidden SSID. It makes me select the "Join Other Network..." in the Airport menu (in the system tray), where I need to input the name of the network, then security type, password and wait for it to connect. This is becoming increasingly annoying to have to do every time I come back to my desk.
I'm running Mac OS X 10.5 and there doesn't seem to be an option to connect to a specific network, but rather "Preferred Networks." The only network I have set as Preferred that's in range is my home network, and it still doesn't automatically connect. Making the network publicly visible isn't under my control, so I'm stuck with what's currently in place.
Reader's Digest version: How do I make my MacBook Pro automatically connect to a WiFi Network with a hidden SSID without having to "configure" it every time I want to connect?
Automatically connecting to a network with a hidden SSID is a bad idea.
Since your computer cannot passively listen for the SSID broadcast and automatically connect when it sees the SSID (which will not show in the beacon broadcast, since that is how hiding the SSID works), it has to actively send probe packets with the network's SSID, even if it is nowhere near the access point, and wait for a response. This means that, instead of the access point broadcasting its name all the time, you have all computers configured to automatically connect to it broadcasting its name all the time, no matter where they are.
Not to mention that, to be able to roam between several access points with the same SSID, the computer has to know their BSSID (essentially, the AP's MAC address). Usually they do this by listening to the beacons broadcast by the access points. Since the beacons do not have the SSID (hey, it's hidden!), the computer has to periodically send probe requests even if it is already connected to the access point. Making it laughably easy for an intruder to find out the SSID if even one computer is connected to the network. Not to mention the desassociation attacks.
So, it gains almost zero security (it is still way too easy to find the SSID) and loses a bit more security (the client computers constantly announcing to the world "hey, I am a computer belonging to someone who works at company XYZ!" even when nowhere near company XYZ). The net result is negative.
The only way to reduce or even avoid the security loss is to have it connect manually instead of automatically. Which seems to be what Apple is doing. (Windows Vista, from what I recall, warns you of the security issues when you try to set it to automatically connect. The NetworkManager used by most Linux distributions also seems to make you chose the saved connection from a dropdown manually.)
In theory, it would be possible to save the known BSSIDs for each ESSID and only send the probe request when a beacon for one of them is received (that is, when you are near an access point which has in the past been used for that SSID). I do not know why nobody seems to have tried that yet.
I googled, and there are apparently many people in you situation. A promised fix by Apple has never materialized. It seems like the only solution is to unhide the SSID on the router. Please note that nowadays hiding the SSID doesn't protect you from anything.
If you "want" you can use a command script and put it to startup or as launch file in the dock: just go to your terminal and save with the following command (with your SSID and key)
/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport --associate=yourSSID --password=yourkey
Hope this helps some people. If you want to "do" more have a look at:
not sure how to respond specifically to irrational John's comment on Jordan Cataldo's answer, so apologies for the new answer. but -- no, iJohn, you can save this applescript, via Script Editor, to an .app that can be placed in the user's Login Items (under Accounts in System Prefs). then, you'll be logged into the hidden network automatically on startup.
based on Jordan's example, i wrote the following script to login to a hidden network that may not be available yet, for the (admittedly rare) case when the server is on the same power strip as the client, and takes a while to start up. museum exhibits have unusual needs ;)
set networkResult to false
repeat while not networkResult
do shell script "networksetup -setairportnetwork NetworkName networkPassword | /bin/bash"
-- network found and joined.
set networkResult to true
on error errorMsg
-- network not yet available;
-- wait five seconds and try again.
set networkResult to false