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I'm trying to run multiple Nodejs applications on Nginx server running on CentOS 7. I noticed that when I run a Nodejs app on some ports I get an 502 Bad Gateway error in the browser so I checked the error logs:  [notice] 12806#0: signal process started [crit] 12807#0: *13 connect() to 127.0.0.1:7777 failed (13: Permission denied) while connecting to upstream, client: **.**.99.58, server: myapp.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:7777/", host: "myapp.com" [crit] 12807#0: *13 connect() to [::1]:7777 failed (13: Permission denied) while connecting to upstream, client: **.**.99.58, server: myapp.com, request: "GET / HTTP/1.1", upstream: "http://[::1]:7777/", host: "myapp.com"   when I change the app to listen to 8008 for example everything is working fine. I checked permissions and if the process is running as root and everything seems ok. I played with the timeouts as well but no result. Can anyone help? $ \int_{0}^{ \infty} \int_{0}^{ \infty} \frac { e^{-(x+y)}}{x+y} dx dy $ How can I count all the lines of code in a directory recursively? String formatting in Python I want to do something like String.Format("[{0}, {1}, {2}]", 1, 2, 3) which returns:  [1, 2, 3]   How do I do this in Python? In Windows, one can create a new file using Right Click -> Add New -> Type of File. Is there an analogous action in Lion?  I just want to create a new blank file on my Desktop. Stack Overflow provides good tools in the question editor, like "Links" and "Styling".  Another thing that for me would be nice is a color selector. Although an HTML editor is available, a direct click on tool would be good, and users can select different colors, as for marking errors in their program with red, and more important data with blue. Combination with repetitions. The formula for computing a k-combination with repetitions from n elements is: $$\binom{n + k - 1}{k} = \binom{n + k - 1}{n - 1}$$  I would like if someone can give me a simple basic proof that a beginner can understand easily. Why is the detection of gravitational waves so significant? LIGO has announced the detection of gravitational waves on 11 Feb, 2016. I was wondering why the detection of gravitational waves was so significant?   I know it is another confirmation of general relativity (GR), but I thought we had already confirmed GR beyond much doubt. What extra stuff would finding gravitational waves teach us? Is the detection of gravitational waves significant in and of itself, or is there data which can be extracted from the waves which will be more useful? Name finding problem with comment notification feature I just received the following in my Response pane (from ), but you can see it was meant for another user.  The @Robert line seems to have found 'Robert' in my name first, instead of Robert C. Cartaino.  I think the comment notification feature should match based on the closest match from the first character in a name (in posting order), and not just the first match found in posting order. 32-bit, 64-bit CPU op-mode on Linux Rest mass of the photon Why is the rest mass of the photon is taken to be zero?  If rest mass of the photon is non zero, then it leads to infinite energy of the photon (by $E=mc^2$ equation) and there is a violation of conservation of energy. Is this a reason?  Also, is there any thing called the relativistic mass of the photon? Chrome address bar no longer shows protocol or www subdomain A couple of days ago I noticed that for all websites, chrome omits from the address bar the protocol and the subdomain if it is www. My co-workers report that they are not seeing this. Chrome version is 67.0.3396.87.  For example, if I type into the address bar https://www.google.com (without the quotes), Chrome immediately displays the chip "Secure" followed by google.com. See attached screenshots.      I have looked in vain for Chrome settings that affect this, plus the chrome://flags page and chrome://net-internals page.  I did not do anything consciously to make this change.  Any ideas?  EDIT: Suggestion from MrWhite that Ominbox UI Hide Stead-State URL Scheme and Trivial Subdomains had become enabled: good suggestion, except that the setting is still at “Default.” See screenshot:    However, as a shot in the dark, I am going to play with the setting to see what happens.  First I set it to “Disabled.” That restored the previous behavior of the address bar, which is to not to hide the protocol and “trivial subdomains.” Then I changed it back to “Default,” and it was hiding them again. One would suspect that somehow the default has been changed, except that co-workers are not reporting this issue.  Oh, well. I’ll just leave it as Disabled for now.  I would be ready to accept the answer from MrWhite, because it provides a workaround. Yet will leave it open for a bit longer, because it does not really answer why this behavior has changed, and why it has to be overridden.  EDIT 2: Chrome version is 67.0.3396.87. Will I be able to get an interface that is like Gnome Classic in Ubuntu 14.04? For a while I departed from Ubuntu to use Linux Mint because I really don't like Unity, or Gnome 3's most recent interface.  I was fine with what was called "Gnome Classic", but I feared it was being neglected because there were some significant bugs that lingered without improvement for a while.  Unfortunately, while I like the MATE interface in Linux Mint, Mint itself lacks the level of community support that Ubuntu has. Mint has development and support issues. Not to disparage their efforts, I think they've done great work, but it's tough making a UI, and unfortunately it's just not working for me.  I'm thinking of returning to Ubuntu with the 14.04 release, but not if it means using Unity. I have looked into the current situation, and I'm a little confused about the terms being thrown around. I have seen referens to "fallback", "flashback", and "classic", without any clear idea of which is available and what they offer.  Is there still an option to get an interface that resembles the way Gnome used to look?  Can I get an interface that looks like what I have with Mint, but with the support and features of Ubuntu? Can I get something close to that? Upgrade to the latest PHP version in ubuntu 16.04 Can you explain more?  I do not know when we can use them in the sentence.  Can we use them instead of each other?     They have a beautiful home.   They have a beautiful house. Truncated trivariate normal - conditional expectation Cannot set up multiple desktops (workspaces) How do I remove a property from a JavaScript object? Say I create an object as follows: let myObject = {   &quot;ircEvent&quot;: &quot;PRIVMSG&quot;,   &quot;method&quot;: &quot;newURI&quot;,   &quot;regex&quot;: &quot;^http://.*&quot; };  How should I remove the property regex to end up with new myObject as follows? let myObject = {   &quot;ircEvent&quot;: &quot;PRIVMSG&quot;,   &quot;method&quot;: &quot;newURI&quot; }; What's a good back-up strategy for 1 desktop PC? How to easily build your own Linux Distro? I wanted to have a go at creating my very own Linux Distribution. Could you suggest some nice and easy-to-follow tutorials (preferably text based and not videos). I have heard something about Arch Linux but I don't know how to go from there. What do I need?