網際網路軟體 Internet Connectivity

產品包括: Nucleus WebServ, Nucleus Extended Protocol Package (Telnet, FTP, TFTP), Nucleus EMAIL (SMTP, POP3), Nucleus DHCP Server 及 Nucleus SNTP Client

When most people think about networking, they think of the Internet. The Internet has literally changed the way that information is communicated. It has had a profound impact on everything from the way that businesses advertise and promote their products to the way that individuals keep in touch with one another. The Internet ties together much of the population of the industrialized world, and we have all seen the statistics on its growth rate.
 
Some protocols more than others have come to be associated with the Internet. Specifically these protocols include HTTP, the basis for Web Servers and Web Browsers, POP3 and SMTP, the basis for email, FTP and TFTP, file transfer protocols, and Telnet for remote login. Many of the features that make these protocols invaluable to desktop computing, are just as applicable to embedded computing. This site location introduces you to Accelerated Technology™’s embedded versions of these protocols.
 
Nucleus WebServ


With the expansion of the World Wide Web, have you considered making use of its many benefits in your embedded system? By using Nucleus WebServ, you can allow your users to access your embedded system from the powerful environment provided by Web browsers.
 
Nucleus WebServ is an implementation of the HTTP (Hyper Text Transfer Protocol) that is capable of interpreting important information in HTML (Hyper Text Markup Language). These capabilities give your users powerful facilities that will enable them to interact with your target in a dynamic and exciting way.
 
How Does It Work?

Your target is, simply put, a Web server. You may have the concept in your mind of a Web server as a piece of software that resides on a File Server somewhere. That’s essentially true, but it may not serve up files to all users the same way.
 
With Nucleus WebServ, we provide a utility for you to select files on your hard disk and convert them to a C file, which contains the binary representation of the files and an associated directory. This serves as your embedded file system (if you are not already using a traditional file system like Nucleus FILE). In your embedded file system, you can place any files that you would like your users to retrieve from your embedded system.
 
The power of Nucleus WebServ is that it gives you the ability to intelligently use the files that you are serving up to your users. In addition to supplying HTML files in the standard way (i.e., no manipulation of them in any way, they are just sent to the Web browser and displayed), Nucleus WebServ can create dynamic content and respond to function execution requests from the Web browser (probably by a reference in one of the HTML files that are served to the Web browser).



Web Server Capabilities

Traditionally, it’s been difficult to provide an efficient and easy-to-use interface to embedded systems. With the advent of the Web and the ubiquity of Web browsers, Nucleus WebServ supplies you with the ideal tool for communicating with your users. Through static HTML files, dynamic Web pages and remotely executable procedures, you can provide any kind of information about your system. Plus, you don’t have to write specific applications for each prospective operating system. There are many technologies that can improve the usefulness of your system to its users, but none can do it as effectively and affordably as incorporating Nucleus WebServ into your product.

Serve Static HTML Files

The most basic capability of Nucleus WebServ lets you serve standard HTML files to your users on a Web browser without writing any code! By using the utility mentioned previously, you simply select the files you want stored on your target (a manual for example) and click a button to generate the necessary code. That code is then compiled and linked with your application and voila! You are serving pages.

Building Dynamic Pages

One of the more powerful features of Nucleus WebServ is the ability to build dynamic pages. This is very useful for remote monitoring of an embedded device. For example, suppose the embedded device is a Web-enabled soft drink machine. It would be possible to dynamically build a page that consisted of a table showing the flavors of drinks in the vending machine and how many of each flavor remained. Every time the dynamic page is loaded, it would be updated (on your target and sent to the browser) to reflect the new values as drinks are purchased or the machine is refilled.

Executing Functions on the Target

The ability of Nucleus WebServ to respond to function execution requests from a Web Browser can be used in many ways, the most obvious of which is remote control or remote configuration of the embedded device. Continuing the soft drink machine example, suppose the vending machine operator wished to raise the price of a soft drink when the temperature rises above 95 degrees Fahrenheit. It would be possible to have a HTML form embedded in the machine that would allow the price of a soft drink to be configured remotely. So, sitting in his nice cool office, the vending machine operator could load the form, modify the price and submit it back to Nucleus WebServ. The new price would take effect immediately.
 


Nucleus WebServ Features:
 

• Fully functional server in tiny package
   
• HTTP 1.0/1.1 Support
   
• Dynamic Web page content (Allows Monitoring)
   
• Forms support (Allows Configuration)
   
• Content Independent (Serve Java Applets, Images, etc.)
   
• CGI (plugin) support
   
• Server Side Include support (SSI)
   
• File upload (online document update)
   
• Flexible page storage (in memory or on disk)
   
• Supports multiple concurrent requests
   
• Basic authentication
   
• DES authentication
   
• Document compression
   

Nucleus Extended Protocol Package
 
Some of the most popular, and useful, network applications include those that provide for file transfer and remote login. Nucleus Extended Protocol Package (Standard Networking Application Protocols) is a suite of protocols that provides complete support for such applications. Specifically support is included for the File Transfer Protocol (FTP), the Trivial File Transfer Protocol (TFTP) and Telnet. As with all Nucleus products, a demonstration application is provided that shows how these protocols can be utilized to create a custom FTP Client, FTP Server, TFTP Server and/or Telnet server application. Note: TFTP client support is provided as part of Nucleus NET. This demonstration application is an excellent starting point for development of your own applications.

FTP Client/Server

So, what role does FTP play in the Nucleus networking package? As the name implies, hosts send and receive files using FTP. The files can be of any type. Enabling an embedded device with the FTP server allows for remote users to initiate an FTP session with the embedded device. The remote user can then transfer files to and/or retrieve files from the embedded device. The remote user could also issue standard directory and file commands. For example, the remote user could, among other things, list a directory, rename a file, or change directories.
 
Enabling an embedded device with the FTP client provides for the same functionality in reverse. That is, the embedded device initiates a FTP session with a remote FTP server. Once the session is initiated, the embedded FTP client can get and put files as well retrieve a directory listing, and perform other common directory and file commands.
 
As you would expect, FTP requires some type of file system. Utilizing the Nucleus File Abstraction Layer (FAL), provided with Nucleus NET, the FTP client can operate without a physical file medium present. In this configuration Nucleus FAL is configured to use a block of memory as if it were a physical file medium. The FTP Server does require a physical file medium and a true file system to be present. To support the requirement of physical file storage for the FTP server, Accelerated Technology provides Nucleus FILE, our MS-DOS compatible file system. Of course, the FTP Client can also utilize Nucleus FILE.


 
TFTP Server

The Trivial File Transfer Protocol (TFTP) can be used for many of the same purposes as FTP. However, it is more limited in functionality. TFTP uses UDP as the underlying transfer protocol, while FTP uses TCP. UDP is less reliable than TCP, thus TFTP is generally relegated to the transfer of files on a local network, where the chances of packet loss and errors is minimal. In addition, the operations that TFTP can perform are limited to a file get operation and a file put operation. The primary benefits of the TFTP are its size and efficiency in processing. TCP is requires fewer resources than UDP. Also, because of its limited functionality TFTP is smaller than FTP.
 
An embedded application enabled with the TFTP server will provide for remote users transferring files to or retrieving files from the embedded device.



Telnet Server

Telnet allows a terminal to the embedded system to be opened from a remote computer. Utilizing this terminal, you can issue commands to the embedded device, allowing the device to be controlled remotely. Custom commands can be added to the Telnet command parser. In this way Telnet can be customized and extended to parse commands specific to you embedded device.
 
The example application provided for Nucleus Telnet plugs into Nucleus SHELL. Nucleus SHELL is discussed in greater detail below, but basically this demonstration system will allow a remote user to perform runtime kernel aware debugging from a Telnet session. As an example, a user can issue a command to list the tasks that are present, their state (suspended, executing, etc.) stack size, priority, etc.



Nucleus SHELL

Nucleus SHELL was developed to assist users of Nucleus PLUS in debugging their multitasking applications. It installs as a task in any Nucleus PLUS system and provides a number of features designed to complement debugging performed through your debugger. All user interaction with Nucleus SHELL is performed through a command line prompt. The commands are typically issued through a serial terminal application, but when Telnet is present the same commands can be issued from a Telnet session.
 
Nucleus SHELL supports display of information on all Nucleus PLUS kernel objects. For example, you could issue a command to see the status of “task 1”. Discovering “task 1” is suspended on a queue, you could then examine each of the queues to see which of the queues “task 1” is pending on. You can also remotely invoke Nucleus PLUS services. For example, you could push an item onto the queue in order to kick-start “task 1”. Finally, Nucleus SHELL allows memory to be viewed and modified.
 


Nucleus EMAIL

Accelerated Technology offers the Nucleus EMAIL package for those who wish to provide an email client or server in their embedded device. An obvious question is why would someone want enable an embedded device with Nucleus EMAIL. An email client could send logs of information to a server, or an alarm could be sent to an administrator. An email server could be mailed commands or configuration information. Nucleus EMAIL includes support for the two protocols: POP3 and SMTP. When combined, these protocols allow any embedded device to be email-enabled.

POP3

POP3 is the most recent version of the Post Office Protocol, a standard protocol for receiving email. An email client uses POP3 to retrieve email from an email server. In other words when you hit the receive button in Microsoft® Outlook® this is the protocol that does all of the work.

SMTP

Simple Mail Transfer Protocol (SMTP) is the protocol used by a device to send email to an email server. The send button in Microsoft Outlook invokes this protocol. This protocol is also used by email servers to relay email to one another. Email messages are queued in a server mailbox from which they can be periodically checked using POP3. Developers typically use a program that implements SMTP for sending email to an email server and POP3 for receiving messages from an email server.
 


Nucleus DHCP Server

The Dynamic Host Configuration Protocol (DHCP) defines the method by which network hosts can dynamically acquire an IP address, as well as other configuration information. DHCP is a client/server application, with servers responding to the configuration requests of clients. DHCP takes much of the burden out of the administration of local area networks.
 
Nucleus DHCP can enable your embedded device to respond to the configuration requests of DHCP clients, typically PCs. An example application of Nucleus DHCP Server would be for use in a residential gateway. This would allow the gateway to not only perform its routing duties, but to also handle configuration of the hosts on the LAN.



Nucleus SNTP Client

Nucleus SNTP (Simple Network Time Protocol) Client enables your embedded device to retrieve the current time from a time server. This could be used at boot time to initialize a local clock, or it could be used to retrieve the time as needed. Nucleus SNTP client can communicate with both SNTP servers and NTP servers.

*Link to material on Mentor.com