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Aldora L

Aldora L

Add New User with SSH Access to AWS EC2 and Grant Superuser Access

Add a new user with SSH access to AWS EC2 Linux instance, and grant superuser access through the wheel group. Note: You need a user account which already has the superuser access, such as "ec2-user". Contents * Create a key pair using Amazon EC2 * Add a new user to

PHP Non-blocking Socket with Server-Client Communication: Part 2

In PHP Non-blocking Socket: Part 1, I use foreach to loop through sockets to get the message, but this is an inefficient way which consumes many resources of computers, there is a more elegant way to do this: socket_select. Example Code server client The client code is as same

PHP Non-blocking Socket with Server-Client Communication: Part 1

Example Code In PHP Blocking Socket, I introduced the concept of blocking socket. Now, I would unpack the 'unblocking socket'. With unblocking sockets, we don't need to "wait" as in blocking sockets, also don't need to wait for the completion of the

Java Generics Interface with List

Wildcards How to write a generic interface with List or Collection of implemented class of the interface? I encounter to this problem when I write a tree node interface, here is the details of the problem: I need to create an interface for the following two classes, how to write

Java Variables Hiding and Method Overriding

Method Overriding and Variable Hiding In Java, methods are overridden, but variables can only be hidden. In the case of method overriding, overriding methods completely replace the inherited methods but in variable hiding, the child class hides the inherited variables instead of replacing them which basically means that the object

PHP Blocking Socket with Server-Client Communication Example Code

Outline * PHP Blocking Socket * Example Code * Example Code Breakdown * References PHP Blocking Socket Socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network[1]. Briefly, a socket is an endpoint in an computer to

Apache CollectionUtils subtract and removeAll difference

Maven Dependency <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-collections4</artifactId> <version>4.1</version> </dependency> Difference between subtract and removeAll You can use CollectionUtils.removeAll(collection, remove) or CollectionUtils.subtract(collection, remove) to