concept

It is the mechanism that the browser uses to retrieve any resource published on the Web. URL is a Uniform Resource Locator. A URL is nothing more than the address of a given unique resource on the Web. In theory, every valid URL points to a unique resource. This resource can be an HTML page, a CSS document, an image, and so on. In practice, there are a few exceptions, the most common being a URL that points to a resource that doesn’t exist or has been moved. Because the resource rendered through the URL and the URL itself are handled by the Web server, the owner of the Web server needs to carefully maintain the resource and the URL associated with it.

The composition of the URL

Protocol + domain name or IP+ port + path + query string + anchor form a URL that allows access to a service deployed on a server. For example: http://www.example.com:80/path/to/myfile.htmlkey1=value1&key2=value2#SomewhereInTheDocument

The relevant knowledge

  • IP: each computer has a specific IP address, network has points of private network and public network and private network exists in the local area network (LAN), the computer will not be able to direct communication between different local area network (LAN), the public is equivalent to put all together into local area network (LAN), including through a router to identify, in this way to achieve the communication between different local area network (LAN).
  • Port: There are more than 60,000 ports on a computer. An application will occupy one or more ports. Different services can be published on a computer through IP+ port
  • DNS, DNS server, domain name is inaccessible, the server is unable to identify, but when using IP due to more complicated to memory, so it appeared a DNS, first of all, will be a server binding domain, when use the domain name to access a service, first of all domain names into IP addresses, then find the corresponding server. You can use nslookup to query DNS records to check whether domain names are resolved properly and diagnose network faults.
  • Ping: the value is in the format of ping IP address or domain name, which is used to determine whether an IP address can communicate.