How to access a private network behind a router? Can't port forward I have a video surveillance system (a bunch of IP cameras, with private IPs) behind a router in a distant location. The only ISP that's available at that location has provided me with a 3G/4G USB dongle (so basically mobile Internet). Apparently this dongle (which connects to the router) does some routing/magic by itself (and is not configurable) so I can't use the router to do port forwarding (not in anyway that helps at least). This means that while the cameras have Internet access (so can push information to me), I can't access them directly over the Internet (so basically, no live feeds).  I'm thinking of getting around this by putting a low power computer (software doesn't really matter much in this question, but I'll use Linux) in the same subnet as the IP cameras - let's call this computer A; I also have a VPS rented somewhere that is publicly accessible via the Internet - let's call it B.  I think that this setup should allow me to work around the issue with my live feeds. At least conceptually if I get A to open a tunnel to B then via B I should have access to A's network.  Presuming the above works (I don't see why not, but .. that's why I'm asking) can you guys recommend a system that can accomplish the above with at little fuss as possible? I mean .. should I set-up a VPN with A as a VPN client and B as a VPN server; then anyone who wants to view the cameras simply connects to the VPN server installed on B?  I think this should work, but maybe there's an easier way than setting up VPN on every computer from where I want to check the cameras.  I'm not directly interested in the software (I'm sure that exists and I'll manage to configure it) but rather the networking concepts.   The ideal situation would be that I'd connect to B on (for example) port 8080 and that traffic will automatically be routed from B through a tunnel to A, at which point A will feed data obtained from camera "1" through that connection; then 8081 from camera "2" and so on.
ssh to private-ip I have a computer with CentOS (computer A) that configured as has an private ip 10.150.5.141 (with restricted firewall), can access internet and my ArchLinux VPS (computer B) with real ip w.x.y.z  How can I make another pc (computer C) that could access computer B to connect to computer A, but computer C cannot connect to computer A directly (because it's on A's own private network)?  I know that a tunnel can open local ports to another computer:port, but how to do the opposite?  I want to access computer A using ssh through computer B but computer B cannot access computer A, because the network on computer A is restrictive (can go out, but can't go in, because I have no access to their router)  I want something like this:  ssh -connect-to w.x.y.z:22 -open-port vvv -forward-to 10.150.5.141 -port 22   so that when I ssh w.x.y.z:vvv from computer C it will forwarded to private network 10.150.5.141:22.
NetworkManager not populating resolv.conf Proof that $\frac{a^2}{b} + \frac{b^2}{c} + \frac{c^2}{a} \geq a+b+c$ I've tried getting everything on the left side and transforming it into something squared so that I can prove it's bigger or equals to 0 but I've been unsuccessful. In a bash shell script, writing a for loop that iterates over string values Creating a single index from several principal components or factors retained from PCA/FA I am using Principal Component Analysis (PCA) to create an index required for my research. My question is how I should create a single index by using the retained principal components calculated through PCA.  For instance, I decided to retain 3 principal components after using PCA and I computed scores for these 3 principal components. What is the appropriate ways to create, for each respondent, a single index out of these 3 scores?   Is it relevant to add the 3 computed scores to have a composite value? Or to average the 3 scores to have such a value?  Or should I just keep the first principal component (the strongest) only and use its score as the index?   Alternatively, one could use Factor Analysis (FA) but the same question remains: how to create a single index based on several factor scores? I'm using the built in Screen Sharing tool in El Capitan to control an iMac from a Macbook Pro in full screen mode. Everything works beautifully except that many special keys and gestures are intercepted by the local Mac and not sent to the shared Mac. Specifically:   Ctrl-Arrow (Desktops and Mission Control) F3 (Mission Control) F4 (LaunchPad) Three finger swipe (Switch between Desktops, Mission Control, Exposé) Two finger swipe from left side (Notification Center) Pinch with four fingers (Launchpad)   I can't find any way to switch between desktops on the remote machine other than manually opening the Mission Control app from the Finder or Dock. Disabling the gestures on the local machine doesn't help; they still don't get sent to the remote machine.  Is there any way to get special keys and gestures passed to the shared machine? PythonTEX not working on current Overleaf compiler Is there a way to make PythonTEX compile as of today in Overleaf V2 ?  \documentclass[]{article} \usepackage[utf8]{inputenc} \usepackage{pythontex}  \begin{document} \begin{pyverbatim} def calc_ellipticity(theta, delta):     theta = np.deg2rad(theta)     psi = np.arcsin(np.sin(2*theta) * np.sin(delta))/2     return np.tan(psi) \end{pyverbatim} \end{document}   Compiling gives : ? PythonTEX ? I flagged a question, , as "low quality" but a moderator declined it. I thought that the post was a low quality one and would like to know why the moderator did not.  Hopefully shedding light on this matter will avail me of the knowledge to be a better flagger in future.  My logic was that mysql-fetch-row is not supposed to return an array of results. If it does than its name would be mysql-fetch-rows.  What's your take on the situation? Preserving signatures of decorated functions How to determine which window manager is running Is there any way (such as a command or environmental variable) to determine what window manager is the one actively running in the current session? $n$ balls are thrown randomly into $k$ bins - how many are empty? A large number of variants of this question were already asked here, including these - , , which are close, but none seem to answer my question. Assume that $n$ balls are thrown randomly and independently into $k$ bins.  What is the probability of finding $x$ empty bins? What is the expectation of the number of empty bins? How does a wavefunction collapse into one state? More specifically, what conditions cause a wavefunction for a quantum particle to collapse?    Does this have to do with density matrices?    Please try to give a mathematical explanation that is simple and concise... I recently saw a lecturer prove the following theorem (assuming the result that every analytic function is locally 1-1 whenever its derivative is nonzero): Let $\Omega \subset \mathbb{C}$ be open, and let $f : \Omega \to \mathbb{C}$ be 1-1 and analytic on $\Omega$.  Then $f&#39;(z_0) \not = 0$ for every $z_0 \in \Omega$.  I got the basic idea behind the proof: we assume for contradiction that $f&#39;(z_0) = 0$, and, assuming without loss of generality that $z_0 = f(z_0) =0$, we have (from the power-series expansion) that $f(z) = z^kg(z)$ for some analytic $g$ in some disk at the origin (i.e., $z_0$) and some $k \ge 2$. Since $z^k$ is not 1-1 in any such disk (because there are multiple roots of unity), then $f$ isn't either.  However, the proof he gave was rather awkward and technical- it involved defining three different axillary functions, even though the idea was simple, and I've since forgotten how it exactly worked.  In any case, I'm convinced there's a better way.  The problem is that I'm having trouble turning the idea into a real proof- I know that it obviously follows if $g$ is 1-1, but I'm also pretty sure that that is too strong an assumption.  Am I missing something, or does the argument just have to be more complicated? What is the difference between \big[ (or equivalently \big() and \bigl[? Is it always necessary to mention l (left) and r (right)? Getting user provided data out of a database and into R While I understand the intuition behind expectation, I don't really understand the meaning of variance and moment.   What is a good way to think of those two terms? In my document, I will write something like this (using natbib, but that shouldn't matter too much):  \citet{reference} show that .....   which would render as     Jones et al (1990) show that....   (\citet in \natbib creates an 'author-list (year)' reference style)  Of course if {reference} was a single individual, I should have written  \cite{reference} shows that ....   rendering as     Jones (1990) shows that....   Since I'm lazy and can't take the extra 5 seconds to search the reference to see if it's a single author or not, is there conceivably an automated way to do pluralization ? Or some relatively simple macro that would look like   \IfRefIsPlural{reference}{show}{shows} I am trying to determine if the sum $\sum_{n=1}^\infty \frac{n+4^n}{n+6^n}$ is convergent or divergent.   In attempting to solve this problem I began by seeing if I could do the divergence test - in this case it is not helpful. The terms $4^n,6^n$ look like geometric series type terms but the $n$ in the numerator and denominator are troublesome. I first tried factoring $n$ out of the expression:  $$\sum_{n=1}^\infty \frac{n+4^n}{n+6^n} = \sum_{n=1}^\infty \frac{1+\frac{4^n}{n}}{1+\frac{6^n}{n}}$$  Next I tried comparing to the series $$\sum_{n=1}^\infty \frac{\frac{4^n}{n}}{\frac{6^n}{n}} = \sum_{n=1}^\infty \frac{{4^n}}{{6^n}} = \sum_{n=1}^\infty{\left(\frac{2}{3}\right)}^n$$  This is a convergent geometric series as $r = \frac{2}{3}\lt1$  now I reason that the series $\sum_{n=1}^\infty \frac{1+\frac{4^n}{n}}{1+\frac{6^n}{n}}$ is neither smaller not greater than the series $\sum_{n=1}^\infty{(\frac{2}{3})}^n$ Am I able to conclude anything in this case by a direct comparison test or can I only conclude that the first series is convergent if the second is greater than the first?  Thanks If asking a question or giving instruction towards a group of objects where the number is unknown (and possibly could be one) what is the correct way to phrase the sentence? Which of the following sentences are more correct:     Has there been any studies regarding this and if so what has been the   conclusion?   OR     Has there been any studies regarding this and if so what have been the   conclusions? I have been reading Stack Exchange for years - mostly not logged in, and have never posted (this is my first). I'm simply not very talkative, and very good at googling.  Recently a few occasions have come up when I've wanted to comment on a question.  I wanted either to ask for, or provide, clarification which did not warrant a new answer.  How do I gain enough reputation to comment without:   asking questions which have already been answered or that I can figure out on my own, or posting my comment like as an answer (i.e. being  rude)? I was wondering about the reason of the choose of the X as symbol used to represents the "Close application" operation.