An Introduction About Proxy Server

proxy servers

Proxy / proxy server

A proxy is a service that serves as a cache within a network to service accesses to always the same data and files from memory.

The term proxy refers to a server or service running on a server. The proxy service is a program that works in the background on a server.

Proxy means proxy. In the simplest case it is a kind of cache for websites. He accepts requests from clients and evaluates them. As a representative, he forwards the request to the Internet.

The returned data is stored by the proxy before forwarding. In the case of another request for the same destination, the data is not downloaded from the Internet, but sent directly from the proxy memory to the recipient. In this way, traffic to the Internet is saved. This reduces costs and increases bandwidth for other applications.

Standard Proxy

The clients do not send their access directly to the internet, but to the proxy. This server acts as a mediator to connect to the web server. Frequent Internet pages or downloads then no longer need to be re-transmitted over the Internet, but can be sent directly from the proxy server to the clients. This reduces data traffic to the Internet and returns the data to the clients faster.

Reverse Proxy

The reverse proxy works the other way around and is similar to load balancing. For example, the clients access the Internet without a proxy. A group of web servers is hidden behind a proxy. The web servers are not directly accessible.

The proxy does not forward frequent identical accesses from the Internet to the web server, but works it off itself if it has cached the data.

So a simple load distribution is possible, without expensive or complicated load balancing. Reverse proxies can also prevent unauthorized access.

In another application, the access authorization for multiple servers is handled centrally by a proxy.

Advantages

  • Faster access to always the same data
  • Cost savings on Internet traffic
  • Integration of virus and spam filters possible

A proxy provides more protection for systems that communicate through a proxy rather than directly to the Internet.

Unnecessary packets from external computers no longer reach the local network because the proxy can only forward accesses from the Internet if an outgoing connection has previously existed.

In addition, a virus filter can be installed on the proxy. To be able to work effectively, every internet access must be done via the proxy. This is achieved by the fact that the default gateway is not the router to the Internet, but an upstream proxy.

Disadvantage

  • Cache coherency due to outdated content in the cache
  • Not every application supports proxies
  • There are not proxies for every Internet protocol

The disadvantage of proxies is that a proxy must be installed for each Internet protocol if all the traffic is to be handled via the proxy server.

This means the proxy program must be able to handle all the possible protocols that the Internet has to offer. It’s not enough just to support HTTP to access web servers. Also POP and SMTP for the E-Mail communication must be mastered.

Typically, the programs on the clients must support traffic through a proxy. This is not a problem with simple Internet services, such as WWW and e-mail. But online games and P2P file sharing will be difficult or not work at all.

Conclusion

Proxies have been a means for Internet service providers to save traffic in the early days of the commercial Internet.

At that time, the Internet connections were even slower and more expensive. In addition, many Internet users were still on the road with a modem or ISDN card. To deliver the data faster, proxies have been set up to serve customers faster and save traffic.

Meanwhile, the network expansion of the Internet is designed very generously, so that a proxy offers no benefits.

Exceptions are transitions from local networks to the Internet, where a proxysite is used for security reasons. On the one hand, to limit the possibilities of the users.

And second, to check traffic for malicious content, such as viruses and worms. It’s usually about protecting the local network.

An Interesting Article About Proxy Site Working

proxy coding

If I access the A website through a proxy, for A, it treats the proxy as a client, completely undetectable of the real client, which achieves the purpose of hiding the client IP.

How The IP Changed By Using Proxy Site

Of course, the agent can also modify the HTTP request headers, by X-Forwarded-IPtelling a true client server IP such as custom head. However, the server can not verify that this custom header was actually added by the proxy or the client modified the request header, so extra care should be taken when getting the IP from the HTTP header field. This part can refer to my previous ” HTTP request header X-Forwarded-For ” article.

Explicitly designated browsers

Explicitly designated browsers to the browser, you need to manually modify the browser or operating system settings, or specify the PAC (Proxy Auto-Configuration, automatic configuration file) automatically set, and some browsers support WPAD (Web Proxy Auto discovery Protocol, Web Proxy auto-discovery protocol). Explicitly specify the browser proxy This method is generally called forward proxy, the browser enables the forward proxy, the HTTP request message will make some changes to avoid some of the problems of the old proxy server, this part can refer to My previous ” Http request header Proxy-Connection ” this article.

Resolution To The Proxy Server IP

Another situation is that when visiting A website, the actual visit is the proxy. After the proxy receives the request message, it sends a request to the server that actually provides service, and forwards the response to the browser. This situation is generally referred to as reverse proxy, which can be used to hide server IP and port. After the general use of reverse proxy, you need to resolve the DNS domain name resolution to the proxy server IP, then the browser cannot detect the existence of the real server, of course, do not need to modify the configuration. Reverse Proxy is the most common way to deploy a Web system, such as this blog is to use Nginx’s proxy_passfeatures will forward the request to the browser behind Node.js service.

youtube-chain

Coding

After the above code is run on the local 8888open port for the HTTP proxy service that parses the request URL and other necessary parameters from the request message, the new request to the server and forwards the request agent received a new request, final Then the server response back to the browser. Modify the browser’s HTTP proxy to 127.0.0.1:8888access the HTTP Web site and then, agents can work properly.

However, after using proxy site, the HTTPS website is completely inaccessible. Why? The answer is very simple, this agent provides HTTP service, and there is no way to carry HTTPS service. So whether this proxy to HTTPS on it? Obviously not, because the essence of this proxy is a middleman, and HTTPS site certificate authentication mechanism is hijacking nemesis nemesis. In normal HTTPS service, the server does not authenticate the client’s certificate. The middleman can successfully complete the TLS handshake as the client and the server. However, the middleman does not have the private key of the certificate. In any case, the server cannot establish a TLS connection with the client. Of course, if you have a certificate private key, the proxy certificate corresponds to the HTTPS website of course no problem.

What is Proxy Site and How It Works?

proxy linkage

What is Proxy site?

Web Proxy Server, known as an online proxy or online proxy. Web page proxy is a child of proxy server program running on the web page.

Without any setting, the advantages of accessing the Web server by selecting the Web address have become the most popular proxy access method nowadays.

A web proxy is a common child of the agent. The web proxy provides the client with a cache of web pages and files on the remote site so that the client can browse the remote site more quickly and securely.

Some web proxy sites keep updating daily to ensure speed.

Is Proxy Is A Middle Linkage For Boosting Web Speed?

Web proxy principle is to receive the browser to the remote site browsing time, the agent started to look at the current server cache Web site is returned to the user’s browser client.

If the current server does not cache the remote server, the agent automatically reads the remote site, submits the data to the client, and caches the data for the next browsing requirement.

The agent automatically deletes the cache based on cached time, size, and fetch records.

There are two ways to delete, one is to delete the oldest data, and one is to delete the least extracted cache. These two methods can, therefore, be used in combination.

Web proxies use different and complicated scripts to bypass filters and firewall websites.

Users using online proxy services are very simple, do not need to be a browser, and do not need to install additional software, just visit the online acting websites, and then you can enjoy free agency services.

In mainland China, some sites are blocked, web proxy access can be viewed.

Advantages of Web Proxy

A web proxy is a web proxy with the function of the anonymous proxy server. When an online proxy is running on the server, the web proxy can be used as a springboard to surf the Internet. It does not only make the Internet more secure.

The web proxy can filter the content of remote sites. Some censorship software is similar to the web proxy.

For some purposes or protection, some web agents are so far the content of the site. For example, Skweezer can reschedule pages to provide browsing for mobile and PDAs.

Network administrators thus often use agents to prevent virus and reaction site content.

These programs are usually written in PHP or CGI programming language. An agent written by CGI is often used to break the network blockade of a company or school.

Agents wrote through CGI hide the client’s IP, so users can anonymously access remote sites.

The proxy written by PHP uses 64-bit encryption technology, uses the fsockopen function to access the target URL through the HTTP access class, and then processes the HTML code and prefixes each link thereafter And CSS, Javascript files.

Through some web proxy download software, you can filter out some dangerous files containing viruses and Trojans, which can make the browsing experience more secure.