SEARCH KEYWORD -- Linux server


  gethostbyname vs getaddrinfo

getaddrinfo is slower than ping when resolving domain names. I think ping uses gethostbyname to resolve a domain name. The question becomes whether getaddrinfo is slower than gethostbyname. After testing with both functions, we find that getaddrinfo is really slow compared to gethostbyname. By strace tracking,  we find getaddrinfo will communicate with DNS server 10 times and gethostbyname will communicate with DNS server communication twice.gethostbyname is an old way to resolve domain nam...

   C++,network,DNS     2012-08-15 14:06:34

  New HTTP status code: 451 Unavailable for Legal Reasons

On June 11th,2012, Google proposed a new HTTP status code to indicate webpage contents which are not conform to law. The new HTTP status code is 451 Unavailable for Legal Reasons. Google Android Developer Advocate Tim Bray submitted the draft for the new HTTP status code, it will be used on some webpages which can not be served because of legal reasons. Visitors will know that the page cannot be seen because of the government censorship.According to the draft, responses using this status code sh...

   HTTP status,451,Tim Bray     2012-06-12 09:07:44

  How to use xargs command in Linux

What is the xargs command? The xargs command constructs and executes commands provided through standard input. It takes input and converts it into command arguments for another command. This functionality is particularly useful in file management and can be combined with commands like rm, cp, mkdir, and others. Using the xargs command When used alone, the xargs command prompts the user to enter a text string and then passes it to the echo command. This example demonstrates the input provided an...

   XARGS,LINUX     2023-11-17 11:19:41

  What you may not know about PHP session

When we access one website, the site usually should have a mechanism to keep track of the status of the user on the site. There are a few mechanisms supported by many server side languages to help track user status such as session and cookie. Today we will talk about session, when creating a session, we need to keep track of many data, besides user data, we also need to tell the server what is the timeout of the session so that we can garbage collect the session data which should not be stored a...

   PHP session,session timeout,example     2013-07-06 08:44:18

  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

  Send email using PHPMailer on GoDaddy hosting

According to PHPMailer troubleshooting guide, GoDaddy has a very strict rule on sending email using PHPMailer. Popular US hosting provider GoDaddy imposes very strict (to the point of becoming almost useless) constraints on sending an email. They block outbound SMTP to ports 25, 465 and 587 to all servers except their own. This problem is the subject of many frustrating questions on Stack Overflow. If you find your script works on your local machine, but not when you upload it to GoDaddy, ...

   PHP,PHPMAILER,GODADDY     2018-11-16 08:28:55

  Common usage of ls command in Linux

In Linux, ls might be one of the most frequently used commands. It is used to list files in a specific directory. In most cases, we may just use ls -l to list the files under a directory. But have you explored other usages of this command. In this post, we will summarise some other common usages of ls command Assuming we have below directory structure in our system, let's see them using tree command. List details of the files If we want to list the details of the files in /home/alvin/test_...

   LINUX,SHELL,LS     2018-12-16 03:00:42

  How to do pprof for gRPC service

gRPC is a RPC framework based on HTTP and is frequently used for communications among micro service inside the same organization network. However,  the service functions cannot be accessed via normal HTTP URL as it's not a WEB framework. In this case, how to do pprof on a gRPC service? The trick is starting a HTTP server asynchronously while starting the gRPC service. This HTTP server can be accessed to run prrof debug. go func(){ http.ListenAndServe(":10001", nil) }() Since it uses the de...

   GOLANG,PPROF,GRPC     2021-01-29 23:11:33

  FTP active mode and passive mode

1. What's active mode and passive mode a. FTP has two ports to control: Port 20 is for data transfer Port 21 is for control or establish TCP connection b. The process of active connection Note: C represents Client and S represents Server S opens port 20 and 21 C connects to port 21 of S with a random port, this port can be between 1024 and 65536, it sends port+x to server at the same time to specify C(X)->S(21) When S receives the command, it will sends back ACK, S(21)->C(X) S will set ...

   FTP,Active mode,Passive mode     2013-04-01 07:01:25

  Apache Tomcat Installation and Configuration

When you want to install Apache Tomcat on Windows System. You may find that there are some tricky parts. Next I will elaborate the steps to install and configure Tomcat. If you want to install Tomcat as a service without GUI. You need to download the 32-bit Windows.zip from http://tomcat.apache.org/download-70.cgi. After downloading this zip file. You need to unzip this file to the directory which you want to put this software to. After unzipping, you can go to the bin directory and find t...

   TOMCAT 7,WINDOWS,APACHE,INSTALL,CONFIGUR     2011-04-10 14:17:21

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