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[miauw62]

Can't MAC adresses be spoofed fairly easily, though? Sure, a homebrew solution in a hotel might not care about that, but some ISPs have these open hotspots built in wherever they can (e.g. with all their customers), and I can't imagine those would like people spoofing the traffic of paying customers.

[i2amroy]

Can't MAC adresses be spoofed fairly easily, though? Sure, a homebrew solution in a hotel might not care about that, but some ISPs have these open hotspots built in wherever they can (e.g. with all their customers), and I can't imagine those would like people spoofing the traffic of paying customers.

Why would you want to though? Unless you change to an address that's already authenticated (in which case all sorts of things could go terribly wrong due to duplicate MAC addresses on the same network) then it's just going to mean that you are forced to redo authentication. This isn't a "blacklist" type of situation, it's a "whitelist" one; so by default you are automatically denied unless you've verified your address and are still using the MAC that you did that with.

[Telgin]

When you log in to public wi-fi, often there's a landing page with a button you have to press before it'll let you actually connect to the Internet. How is this done? I assume it's the local network serving its own page to a new user when it first requests something, but what is the more specific answer?

i2amroy covered some ways that this works, and redirects are how we handle it at work.  We use firewall redirects for all web traffic destined outside of our network if devices haven't gone through registration.

As for how it works on the client side, most devices have specific websites that they try to contact in order to determine if they have internet access.  If they make a request and get a response back that's different from what they expect, they assume that they're part of a captive network and will display the captive network assistant browser, which then hopefully loads the registration page.

The MAC address discussion is interesting.  You can spoof it, yeah, and we've actually had issues with people doing that on our networks before.  It ends up just making their internet not work though, so it doesn't really help.  Spoofing in those cases was actually done accidentally, because the users had some kind of weird network adapters that had configurable MAC addresses and they came preconfigured with the same MAC addresses.

Interestingly, even though MAC address is the (theoretically) unique identifier for a network adapter, we actually manage network access using IP addresses and firewall rules based on them.  The rules are just updated whenever DHCP leases change.

[miauw62]

Can't MAC adresses be spoofed fairly easily, though? Sure, a homebrew solution in a hotel might not care about that, but some ISPs have these open hotspots built in wherever they can (e.g. with all their customers), and I can't imagine those would like people spoofing the traffic of paying customers.

Why would you want to though? Unless you change to an address that's already authenticated (in which case all sorts of things could go terribly wrong due to duplicate MAC addresses on the same network) then it's just going to mean that you are forced to redo authentication. This isn't a "blacklist" type of situation, it's a "whitelist" one; so by default you are automatically denied unless you've verified your address and are still using the MAC that you did that with.

Fair enough, I didn't consider the consequences of having two devices using the same MAC address on the same network.

[EnigmaticHat]

Can't MAC adresses be spoofed fairly easily, though? Sure, a homebrew solution in a hotel might not care about that, but some ISPs have these open hotspots built in wherever they can (e.g. with all their customers), and I can't imagine those would like people spoofing the traffic of paying customers.

Those ISPs give you an account you have to log into to use the hotspot.  And I believe once you disconnect to reconnect you need to log in again.

[Elephant Parade]

Anybody know how to get the Java scanner (the one included in java.util) to read an inputted string? I can't seem to get it to do so, and the official documentation isn't of any help.

Edit: Apparently == doesn't work properly with strings.

[DragonDePlatino]

When getting input in Java, this is the general way I do it:

Code: [Select]

public void getInput()
{
Scanner console = new Scanner(System.in);
System.out.println("Type \"command1\", \"command2\" or \"exit\" to quit.");

boolean run = true;
while(run)
{
String input = console.nextLine();
switch(input)
{
case("command1"):
// Do stuff
break;
case("command2"):
// Do other stuff
break;
case("exit"):
run = false;
break;
default:
System.out.println("Invalid command: " + input)
break;
}
}
console.close();
}
You create a new Scanner and feed System.in (the command prompt) into it. When you want the user to input something, you call console.nextLine() and store the string. The program will freeze until it receives input, after which you can do a switch-statement on it to handle different commands.

EDIT:
Yes, the == operator does not work on strings. You need to use the String.compareTo() method for that. If you're using an IDE like Eclipse, you can type in the name of a string variable followed by a period. It will automatically suggest all of the methods you can use on that object, with input.compareTo() being an example of one.

[DangerDwarf]

Edit: Apparently == doesn't work properly with strings.

== works with strings, but maybe not exactly in the way you may think

In Java, for each variable that you declared, after allocating it (with the new operator) a reference to the memory location for that allocation is stored inside the variable. Then, whenever you use that variable in your code the program will know where in memory to get the data that you are trying to retrieve.

Example: Very simplified, but see it like this. Imagine you are reading two strings from input as follows:

Code: [Select]

Scanner scan = new Scanner(System.in);
String s1 = scan.nextLine();  //user types Hello
String s2 = scan.nextLine();  //user again types Hello
s1 references a location in memory where the physical bytes containing "Hello" is stored. s2 will similarly reference a different memory location containing "Hello".

Now here comes the interesting part. The == operator compares references to each other, and not the contents of these references. Basically s1 == s2 will check whether both s1 and s2 references the same memory location. In this case, the answer will be false.

String however has an "equals" function that will compare the contents of its memory with another String's contents. In this case s1.equals(s2) will return true, as "Hello" was contained in both of them.

Hope this makes sense. But watch out for the following:

Imagine you didn't read the strings from input but instead declared them as follows:

Code: [Select]

String s1 = "Hello";
String s2 = "Hello";
The result of s1.equals(s2) is obviously true, but surprisingly s1 == s2 also returns true? The reason is that Java was quite smart to see that the contents of s1 and s2 are both the same, and decided to hold this contents in the same memory location for both. Basically, both s1 and s2 will reference the same memory. This is possible because the strings were string constants and their values could be predetermined during compilation (in contrast to the previous example where the values were only available at runtime). So when you deal with string constants, keep the above in mind.

[Mephisto]

Spoiler: Story (click to show/hide)

I'm a Python guy looking for something new. That's what led me to even considering listening to the recruiter who cold-called me regarding a Java job in another state.

We go through the standard recruiter phone screen, I forward my resume (now I can add "converting LaTeX to Word doc by way of HTML and ODT" to it...), and I get an email with a link to a HackerRank test. I despise the way the hiring of developers is handled. I swallowed my pride and did their dog and pony show anyway. I appeared to tick all of the boxes they had in our initial screen and I want out of my current job, so why not. Plus, they're not dead set on hiring a Java person. One of the only companies I've found that knows that any developer worth the title can pick up languages quickly is a grocery store. Who knew.

The entirety of my Java experience can be summed up as "used Java for three years in college and started a few personal projects that stagnated before becoming useful". Pulling on what I learned in my most recent failed project and the handy presence of a secondary computer to pull up docs (Fuck all testing sites that don't allow you to look up docs without failing you. That's not how the real world works), I managed to arrive at what I believe were acceptable solutions to the two coding questions in only an hour and a half of forgetting Java syntax and cursing at the horrid web IDE.

Let's see what happens.

Long story short, Kroger (yes, the grocery chain) is actually a pretty neat place for a developer. Their latest projects revolve around ClickList and Amazon Echo.

[MagmaMcFry]

Fuck all testing sites that don't allow you to look up docs without failing you

Uhm. This is a thing?

[Mephisto]

Fuck all testing sites that don't allow you to look up docs without failing you

Uhm. This is a thing?

I think it's an option in HackerRank. I've heard that some tests fail you if the tab loses focus.

[MagmaMcFry]

Only the tab or also the browser? Because then you could switch to a different browser. If not, then I can't imagine how many people that thing failed because of some random Windows popup notice.

[Mephisto]

Only the tab or also the browser? Because then you could switch to a different browser. If not, then I can't imagine how many people that thing failed because of some random Windows popup notice.

Whatever is available in Javascript. With zero searching, it's probably able to tell if the current document has focus. That means no tabs, no switching windows (new browser or otherwise).

In all likelihood, it's a little lie to prevent people from cheating. I wasn't about to test that, though. I just used a separate computer.

[DangerDwarf]

I had to do an interview on Hackerrank and had no problems searching for info when I got stuck.

In fact, I find it a bit inane if they dont even let you look up the javadocs. Dont even see it as cheating really. Really, its the time limit that is supposed to catch you if you look up too many stuff.

[Shadowlord]

https://medium.freecodecamp.com/the-code-im-still-ashamed-of-e4c021dff55e#.ctux664aw

It starts with:

If you write code for a living, there’s a chance that at some point in your career, someone will ask you to code something a little deceitful – if not outright unethical.
This happened to me back in the year 2000. And it’s something I’ll never be able to forget.