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  Check whether a remote server port is open on Linux

As a system administrator or network engineer or application developer, there is a need to check whether a port on remote server is open so that you can tell whether the service under check is running or not. In this post, we would cover a few methods to check whether a remote server port is open or not on Linux. telnet telnet is the most frequently used command on both Windows and Linux to check port. The simple usage for this command is  telnet [host] [port] When the port is open, the o...

   LINUX,TELNET,PORT,NC,NMAP     2017-12-23 11:45:20

  UDP vs. TCP

Introduction Hi, I’m Glenn Fiedler and welcome to the first article in my online book Networking for Game Programmers In this article we start with the most basic aspect of network programming, sending and receiving data over the network. This is just the beginning – the simplest and most basic part of what network programmers do, but still it is quite intricate and non-obvious as to what the best course of action is. Take care because if you get this part wrong it will have ...

   Game design,Networking,Communication,TCP,UDP,Design     2012-02-27 04:49:53

  bash network interface

Some of us may have seen /dev/tcp/<host>/<port> before, is this a special file system implemented in some BSD kernel? Because there is no /dev/tcp in Linux. Actually, this one is implemented in bash. We no need to rely on wget,nc to do network connection. It's very easy to use this interface: bash-4.2$ cat </dev/tcp/time.nist.gov/13 56188 12-09-18 15:34:26 50 0 0 733.5 UTC(NIST) * bash-4.2$ exec 3<>/dev/tcp/www.w3.org/80 bash-4.2$ echo -e "GET / HTTP/1.0\n\n" >&3 b...

   Bash,Network interface,/dev/tcp     2013-07-20 00:57:52

  Introduction to DTLS(Datagram Transport Layer Security)

Secure communication has become a vital requirement on the Internet. Lots of information transferred through the Internet are sensitive data such as financial transactions, medical information, media streaming etc. To ensure security of data transferred on the Internet, a few secure protocols have been designed including SSL/TLS and IPsec. Many large websites in the world have adopted TLS. Apart from SSL/TLS, there is some other protocol designed to be used in special cases. One of them is ...

   JAVA 9,DTLS,TLS,SECURITY     2016-04-02 05:55:36

  WireGuard VPN Troubleshooting

When you are working as a network/cluster admin for you team to config the WireGuard VPN for other members, you may meet some of the problems below and these are the solution you can try to fix them. ----------------------------------------------------------------------------------------------------------- Problem [1]: The WireGuard handshake request send from the client can be received from the server but the server's response was blocked at some where so the client can not receive serv...

   WIREGUARD,VPN,TROUBLESHOOTING     2021-12-14 09:17:46

  New features in Java 9

Java 9 is planned to be released in March 2017. It will be 3 years since Java 8 was released. Are you still excited about the new features introduced in Java 8 such as Lambda, new Date APIs etc? Now Java 9 is to be released and there are also quite a few fantastic new features to be introduced. Below is a list of major new features in Java 9. Modular system. Java 9 will introduce a brand new modular system to organize Java codes. The modular system will divide different packages into diffe...

   JAVA,NEW FEATURE,JAVA 9     2016-04-05 09:56:01

  PHP to get long running process progress dynamically

Frequently in web applications, we may have a request to the back end system which may trigger a long running process such as searching huge amount of data or a long running database process. Then the front end webpage may hang and wait for the process to be finished. During this process, if we can provide the user some information about the progress of the back end process, it may improve user experience. Unfortunately, in web applications, this seems not an easy task because web scripting lang...

   AJAX,PHP,progress,long process,demo     2012-06-04 07:29:37

  The world's first HTML5 SIP client

This is the world's first open source HTML5 SIP client (May 12, 2012) entirely written in javascript for integration in social networks (FaceBook, Twitter, Google+), online games, e-commerce sites... No extension, plugin or gateway is needed. The media stack rely on WebRTC. The client can be used to connect to any SIP or IMS network from your preferred browser to make and receive audio/video calls and instant messages. The protocol parsers (SIP, SDP...) are highly optimized using Ragel loo...

   HTML5,SIP,CLient,Google     2012-05-21 06:18:34

  Want to be a Java developer?

Java is one of the top 3 programming languages in the world. It can be used to develop both web applications and desktop applications and more importantly it is cross platform--write once, run everywhere. Also, it's easy to pick up. If you want to be a Java developer, please get to ask yourself whether you know below listed topics. This list is summarized by Vivek Vermani, a Senior Java Developer: For a Core Java Developer , Ffollowing topics should be good. OOPs Concepts Abstract Classes and I...

   Java,developer,resource     2014-06-19 06:18:47

  10 tools to make your shell script more powerful

Many people mistakenly think that shell scripts can only be run in command line. In fact shell can also call some GUI components such as menus,alert dialogs, progress bar etc. You can control the final output, cursor position and various output effects. Here we introduce some tools which can help you create powerful, interactive and user friendly Unix/Linux shell scripts. 1. notify-send This command can let you inform the process to send a desktop notification to users. This can be used to send ...

   shell,GUI,zenity     2013-04-05 08:50:41

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