What Every Web Developer Should Know About HTTP By K. Scott Allen_3.what web developer should know?-优快云博客

In fact, these days many web sites try to avoid having any sort of real file name in their URL. For starters, file names are usually associated with a specific technology, like the .aspx file extension for Microsoft’s ASP.NET technology. Many URLs will outlive the technology used to host and serve them. Secondly, many sites want to place keywords into a URL (like having /recipe/broccoli/ in the URL for a broccoli recipe). Having these keywords in the URL is a form of search engine optimization (SEO) that will rank the resource higher in search engine results. Its descriptive keywords, not filenames, that are important for URLs these days.

If we put together everything we’ve learned so far, we know a URL is broken into the following pieces:
<scheme>://<host>:<port>/<path>?<query>#<fragment>

Fortunately, you can still transmit unsafe characters in a URL, but all unsafe characters must be percent encoded (a.k.a. URL encoded). %20 is the encoding for a space character (where 20 is the hexadecimal value for the US-ASCII space character).

To specify content types, HTTP relies on the Multipurpose Internet Mail Extensions (MIME) standards.

HTTP is a request-and-response protocol. A client sends an HTTP request to a server using a carefully formatted message that the server will understand. A server responds by sending an HTTP response that the client will understand. The request and the response are two different message types that are exchanged in a single HTTP transaction . The HTTP standards define what goes into the request and response messages so that everyone who speaks “HTTP” will understand each other and can exchange resources. When a resource does not exist, a server can still reply and let you know.

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The practice of redirecting after a POST is a common web design pattern known as the POST/Redirect/GET (PRG) pattern.

Wireshark is available for OS/X and Windows from http://www.wireshark.org/ . Wireshark is a network analyzer that can show you every bit of information flowing through your network interfaces. Using Wireshark, you can observe TCP handshakes, which are the TCP messages required to establish a connection between client and server before the actual HTTP messages start flowing. You can also see the TCP and IP headers on every message.