how to fix java.net.SocketException: Permission denied on ubuntu I'm using apache mina sshd to produce a ssh server so that users could be able to access a specific system remotely.  here is a part of my code:      SshServer sshd = SshServer.setUpDefaultServer();     sshd.setPort(830);     sshd.setKeyPairProvider(new SimpleGeneratorHostKeyProvider("hostkey.ser"));     sshd.setShellFactory(new ProcessShellFactory(new String[] { "/bin/sh", "-i", "-l" }));     sshd.setCommandFactory(new ScpCommandFactory());     sshd.setPasswordAuthenticator(new PasswordAuthenticator() {         public boolean authenticate(String username, String password, ServerSession session) {             return true;             // just to make sure everything is right             // this will implement later         }     });      sshd.start();   when running this code on windows, this code looks ok, but on linux (Ubuntu 18.04), this error is gotten:  Exception in thread "main" java.net.SocketException: Permission denied at java.base/sun.nio.ch.Net.bind0(Native Method) at java.base/sun.nio.ch.Net.bind(Net.java:455) at java.base/sun.nio.ch.Net.bind(Net.java:447) at java.base/sun.nio.ch.AsynchronousServerSocketChannelImpl.bind(AsynchronousServerSocketChannelImpl.java:164) at org.apache.sshd.common.io.nio2.Nio2Acceptor.bind(Nio2Acceptor.java:59) at org.apache.sshd.SshServer.start(SshServer.java:318)   I know running the program using a port number above 1024 might fix this but the standard port of the kind of application I'm developing is 830. how can I fix this problem? does it need any configuration in my firewall or superuser settings?
Is there a way for non-root processes to bind to "privileged" ports on Linux? It's very annoying to have this limitation on my development box, when there won't ever be any users other than me.  I'm aware of , but none of them do exactly what I want:    (The version in Debian testing, 1.0, only supports IPv4)  (the "nat" table is not yet implemented for ip6tables, the IPv6 version of iptables) sudo (Running as root is what I'm trying to avoid) SELinux (or similar). (This is just my dev box, I don't want to introduce a lot of extra complexity.)   Is there some simple sysctl variable to allow non-root processes to bind to "privileged" ports (ports less than 1024) on Linux, or am I just out of luck?  EDIT: In some cases, you can  to do this.
How is a generator found for a group, both in case of DH & ECDH? C# AutoComplete I notice that modern C and C++ code seems to use size_t instead of int/unsigned int pretty much everywhere - from parameters for C string functions to the STL.  I am curious as to the reason for this and the benefits it brings. Probability of flipping coin What is the probability of obtaining THT before HHH when a toss is tossed sequentially? Could someone solve using state diagram and law of total probability? Vandermonde identity corollary $\sum_{v=0}^{n}\frac{(2n)!}{(v!)^2(n-v)!^2}={2n \choose n}^2$ How does the Wizard spellbook work? How do I determine what spells are in my spellbook when creating a character? Do I simply have a spellbook with all Pathfinder spells? Or if I'm creating a level 6 wizard, do I start knowing all level 6 spells, and then have to learn the rest as I play the game? Call C++ library in C# I have a lot of libraries written in C++. I want to call these libraries from C#, however, I have met many problems. I want to know if there is a book or guideline to tell me how to do that. Why do we say that irreducible representation of Poincare group represents the one-particle state? Only because   Rep is unitary, so saves positive-definite norm (for possibility density), Casimir operators of the group have eigenvalues $m^{2}$ and $m^2s(s + 1)$, so characterizes mass and spin, and It is the representation of the global group of relativistic symmetry,    yes? Steward badge can now be awarded multiple times -- backfill details As we announced in our post on  to the Review Queues, the Steward badge can now be earned more than once per queue. The purpose of this post is not to debate the merits of this decision ( already exists), but to explain the nuts and bolts of how it will be backfilled. This is how it will appear on your profile if you have earned it multiple times:  Once we push the visual design changes live across the network, this is how badge attainment will look on /review/close/stats:  For those of you who have already completed enough reviews to earn multiple Steward badges, we will be retroactively awarding them to you, starting today. The backfill script will run about twice an hour, and your achievements trophy will light up as each one is awarded. For those of you who have done thousands and thousands of reviews, things may be a bit noisy, so we thank you in advance for your patience. It may take up to two days for all of your badges to show up. When using vagrant Stderr: VBoxManage: error: VT-x is not available (VERR_VMX_NO_VMX) I am trying to install open edx with  ubunty 16.04 and I get this error  There was an error while executing `VBoxManage`, a CLI used by Vagrant for controlling VirtualBox. The command and stderr is shown below.  Command: ["startvm", "c60f0594-d584-4e0b-b863-2801168e641e", "--type", "headless"]  Stderr: VBoxManage: error: VT-x is not available (VERR_VMX_NO_VMX) VBoxManage: error: Details: code NS_ERROR_FAILURE (0x80004005), component ConsoleWrap, interface IConsole   this occurs when using vagrant up Why has a circle when the point light through my glass？ I found there is a circle when the point light through my glass material using the circle render.  How could I solve it? Group posts by year, then by month If I type something like this:  {\itshape\LARGE   Dunt venim dolorerosto do odit   ametum vulla conum dolore   conulput in vero od el   Dunt venim dolorerosto do odit   ametum vulla conum dolore   conulput in vero od el }   it results in a block of 4 lines with narrow spacing between the 1st and 2nd line and between the 3rd and 4th line. Line spacing between the 2nd and 3rd line is normal.  I can't fully explaing it to myself so I am looking for a short description for this behaviour. I know for example that with a \par at the end of the text (inside the group), the calculation would correct. But I have no idea why... I am trying to define a proof for  $A \cup B = B$ if and only if $A \subset B$  I started with:  $$A \cup B$$ $$x \in A \lor x \in B$$   but I am unsure on how to continue. Autofill feature isn't iterating numbers properly when using the AVERAGE() formula in Microsoft Excel Prove: If a sequence converges, then every subsequence converges to the same limit. If $A^2\succ B^2$, then necessarily $A\succ B$ I remember reading somewhere about the following properties of non-negative definite matrix. But I don't know how to prove it now.  Let $A$ and $B$ be two non-negative definite matrices. If $A^2\succ B^2$, then it necessarily follows that $A\succ B$, but $A\succ B$ doesn't necessarily leads to $A^2\succ B^2$.  How can you prove it? Thanks! I'm running Apache2 in a docker container, and want to write nothing to the disk, writing logs to stdout and stderr. I've seen a few different ways to do this (,  ) but these seem like hacks. Is there no way to do this by default?   To be clear, I do not want to tail the log, since that will result in things being written to the disk in the container. Is there an invalid pthread_t id? Get users to use the download button instead of right-click save As part of our system, a web application, we have an image viewer. Previously we always displayed the full resolution image but scaled down with CSS to fit the page. For performance reasons we now display a properly scaled version of the image with the option to download the full resolution image with a button under the image.  As part of the users' workflow, they sometimes need to download this full resolution image to submit to another system. The problem is that many users just right-click the image and press "save image as". This used to work fine but now it will instead provide them with a low resolution image. The users don't notice this and this causes problems further down the line. How can we force users away from this behaviour? Sure, we could tell them not to do it but that doesn't feel very scalable. My least bad idea so far is to hijack the right-click in the browser but this is A) not super nice UI and B) not sure to cover all cases.  In short: How can we get users to use the download button instead of saving the low-res thumbnail?