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  ByteBuffer in Java

ByteBuffer is introduced in java.nio since Java 1.4. It provides a way of representing raw structured data such as from a file or from network. It enables fast access of underlying data compared to traditional ways like byte[] Prior to Java 1.4, if you want to represent a structured raw data, you need to create a byte[] and then having a set of checks to delimit the byte array to get the expected tokens. There are three ways to create a ByteBuffer: Wrapping an exiting array by calling ByteBuffe...

   JAVA,BYTEBUFFER,ALLOCATION     2015-07-08 03:17:44

  Server monitoring shell scripts

There are many open source server monitoring software such as cacti and nagios. Besides these, can we write our own shell scripts to monitor them? The shell scripts written by ourselves can fulfill our special requirements better and have a more detailed coverage. Below are some commonly used shell scripts used by Evangelist, an Oracle DBA. 1. Check network gateway traffic #!/bin/bash #network #Mike.Xu while : ; do time='date +%m"-"%d" "%k":"%M' day='date +%m"-"%d' rx_before='...

   Server monitor,CPU,memory,shell     2013-08-30 21:56:14

  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

  Pinterest becomes the 3rd largest social network website in US

Digital marketing services company Experian Marketing Services's latest report shows the picture sharing website Pinterest has become the 3rd largest social network website in US following Facebook and Twitter. Its visits are more than LinkedIn and Google + now.Experian conducted a survey about social networking site visits in March,2012, the results show that visits of Facebook were more than 7 billion  Twitter got 182 million visits, Pinterest 104 million. However, the survey ...

   Pinterest,US,Facebook,Pin     2012-04-10 12:33:03

  How Kafka achieves high throughput low latency

Kafka is a message streaming system with high throughput and low latency. It is widely adopted in lots of big companies. A well configured Kafka cluster can achieve super high throughput with millions of concurrent writes. How Kafka can achieve this? This post will try to explain some technologies used by Kafka. Page cache + Disk sequential write Every time when Kafka receives a record, it will write it to disk file eventually. But if it writes to disk every time it receives a record, it would ...

   BIG DATA,KAFKA     2019-03-08 09:42:57

  HTTP Server development resource summary

This article summarizes some materials, articles and books I used when learning HTTP Server development. Hope this will help you. RFC and standard documents RFC2616 – Hypertext Transfer Protocol — HTTP/1.1 HTTP protocol standard document, it's an essential reference document for all personnel engaged in the development of the HTTP-related projects, careful study is recommended. RFC793 – TRANSMISSION CONTROL PROTOCOL TCP Protocol standard document The WWW Common Gateway Interfac...

   HTTP Server,Book,Article     2012-09-25 22:46:56

  Output a file with HTTP range header in PHP

When downloading a large file, we may encounter some network issues which causes download termination and only part of the file is downloaded. When the network connection resumes next time, we may need to redownload the file again from the beginning. In order to save bandwidth, http provides a Range parameter in its header which can control the file transfer flow. With the range parameter in the header, we can resume the download from where we stop. Here is a piece of PHP code snippet which uses...

   PHP, range,http, file transfer     2013-01-09 05:55:05

  Samijyon : A tablet from North Korea

According to Sina Tech, North Korea Tech posted an article about Samijyon. Samijyon is a model of Android  tablet manufactured by North Korea. You can buy it with $200 in North Korea. Smajiyon's hardware configuration is as good as Samsung and Apple, but it doesn't allow WiFi connection and ordinary North Koreans cannot connect to Internet as well, users can only connect to domestic network of North Korea. On this tablet, there are no built-in Google apps such as Gmail and Google Play. But...

   Samijyon,North Korea,Tablet     2013-08-03 22:01:35

  Are you ready for Facebook's phone?

According  to Sina Tech, Facebook will announce its own phone today in US. They will also release its new Android application. The Facebook phone is manufactured by HTC, the model will be HTC First. This will be a deeply customized Facebook phone, some IT professionals think this phone's name is very similar to HTC's flag model HTC One. This phone may provide a home screen application named Facebook Home. Facebook Home adopts the minimization design, it can display photos in full screen. T...

   Facebook phone,HTC,Facebook Home     2013-04-04 07:01:12

  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

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