電子信息工程外文翻譯--嵌入式web服務(wù)器輕量級(jí)tcpip的移植與實(shí)現(xiàn)

1、<p>　　1900英文單詞，9900英文字符，中文3100字</p><p>　　文獻(xiàn)出處：Chen W, Qiu S B, Zhang Y C. The Porting and Implementation of Light-Weight TCP/IP for Embedded Web Server[C]// International Conference on Wireless Communic

2、ations, NETWORKING and Mobile Computing. IEEE, 2008:1-4.</p><p>　　畢業(yè)設(shè)計(jì)（論文）外文文獻(xiàn)翻譯</p><p><b>　　原文：</b></p><p>　　The Porting and Implementation of Light-Weight TCP/IP for E

3、mbedded Web Server </p><p>　　WEI CHEN, SHU-BO QIU, YING-CHUN ZHANG,</p><p>　　Department of Automation of</p><p>　　Shandong Institute of Light Industry?Jinan, China</p><p&

4、gt;　　Abstract--The development trend of embedded technology need the web/server technology applies into embedded fields and provides a flexible remote device monitoring and management function based on Internet browser.

5、But, due to the limitation of hardware resource and the low-efficiency of general purpose TCP/IP protocol stacks and protocol models, it is quite difficult to implement full TCP/IP protocol into embedded system when acce

6、ssing to Internet. The paper analyses the Light-Weight TCP/IP and</p><p>　　Keywords--LwIP; embedded technology; web/server; UC/OS- II; </p><p><b>　　Porting</b></p><p>　　

7、IINTRODUCTION</p><p>　　The traditional Internet web/server is the fat server/thin client, this mode is perfect when translate and store abundance of data, but doesn't behave excellent in embedded field.

8、 And the Internet has become one of the most important basic information facilities in the world, the WWW service it offers has become one of the fastest growing and widest applied service, which have a great deal of adv

9、antages such as visualization, easy remote accessing, multi data format supporting, platform independ</p><p>　　But, due to the limitation of hardware resource and the low-efficiency of general purpose TCP/IP

10、 protocol stacks and protocol models, it is quite difficult to implement full TCP/IP protocol into embedded system when accessing to Internet. Therefore, we need to port a subnet of TCP/IP into the embedded system. In or

11、der to ensure the real-time character and the reliability, we also need to port the µC/OS- II. Considering the limitation of time and performance, it is better to use the exited reduce</p><p>　　lwIP[2](

12、Light-Weight Internet Protocol) is a small independent implementation of the TCP/IP protocol suite that has been developed by Adam Dunkels at the Computer and Networks Architectures (CNA) lab at the Swedish Institute of

13、Computer Science (SICS). The focus of the lwIP stack is to reduce memory usage and code size, making lwIP suitable for use in small clients with very limited resources. lwIP features:</p><p>　　– IP (Internet

14、 Protocol) including packet forwarding over multiple network interfaces</p><p>　　– ICMP (Internet Control Message Protocol) for network maintenance and debugging</p><p>　　– UDP (User Datagram Pr

15、otocol) including experimental UDP-lite extensions</p><p>　　– TCP (Transmission Control Protocol) with congestion control, RTT estimation and fast recovery/fast retransmit</p><p>　　– Specialized

16、 raw API for enhanced performance</p><p>　　– Optional Berkeley-alike socket API</p><p>　　– DHCP (Dynamic Host Configuration Protocol)</p><p>　　– PPP (Point-to-Point Protocol)</p&

17、gt;<p>　　– ARP (Address Resolution Protocol) for Ethernet</p><p>　　IIANALYSIS OF LWIP</p><p>　　A. IP processing</p><p>　　lwIP implements only the most basic functionality of

18、 IP. It can send, receive and forward packets, but cannot send or receive fragmented IP packets nor handle packets with IP options. For most applications this does not pose any problems.</p><p>　　1) Receivin

19、g packets</p><p>　　For incoming IP packets, processing begins when the ip_input() function is caiied by a network device driver. Here, the initial sanity checking of the IP version field and the header lengt

20、h is done, as well as computing and checking the header checksum. Next, the function checks the destination address with the IP addresses of the network interfaces to determine if the packet was destined for the host.<

21、;/p><p>　　2) Sending packets</p><p>　　An outgoing packet is handled by the function ip_output(), which uses the functionip_route() to find the appropriate network interface to transmit the packet o

22、n. When the outgoing network interface is determined, the packet is passed to ip_output_if() which takesthe outgoing network interface as an argument. Here, all IP header fields are filled in and the IP header checksum i

23、s computed. The source and destination addresses of the IP packet is passed as an argument to ip_output_if().</p><p>　　B. ICMP processing</p><p>　　ICMP packets received by ip_input() are handed

24、over to icmp_input(), which decodes the ICMP header and takes the appropriate action. ICMP destination unreachable messages can be sent by transport layer protocols, in particular by UDP, and the function icmp _ dest_ un

25、reach() is used for this. The ICMP processing is shown in Fig. 1.</p><p>　　C. UDP processing</p><p>　　UDP is a simple protocol used for demultiplexing packets between different processes. The st

26、ate for each UDP session is kept in a PCB structure. The last two arguments recv and recv_arg are used when a datagram is received in the session specified by the PCB. The function pointed to by recv is called when a dat

27、agram is received.</p><p>　　Due to the simplicity of UDP, the input and output processing is equally simple and follows a fairly straight line (Fig. 2). To send data, the application program calls udp_send()

28、 which calls upon udp_output(). Here the necessary check-summing is done and UDP header fields are filled. Since the checksum includes the IP source address of the IP packet, the function ip _route () is in some cases ca

29、lled to find the network interface to which the packet is to be transmitted. The IP address of this n</p><p>　　D. TCP processing</p><p>　　TCP is a transport layer protocol that provides a reliab

30、le byte stream service to the application layer.</p><p>　　The basic TCP processing (Fig. 3) is divided into six functions; when an application wants to send TCP data, tcp_write() is called. The function tcp_

31、write() passes control to tcp_enqueue() which will break the data into appropriate sized TCP segments if necessary and put the segments on the transmission queue for the connection. The function tcp_output() will then ch

32、eck if it is possible to send the data, Input processing begins when ip_input() after verifying the IP header hands over a TCP segm</p><p>　　III PORTING OF LWIP BASED ON Formula</p><p>　　The p

33、orting of Formula [4] is very easy now, so I talk about the porting of lwIP on it directly.</p><p>　　lwIP had put the portion about hardware, OS, compiler under/src/arch. Our main task is to perfect the file

34、s under that directory and seldom modify the other files in the porting. In this porting, the realization of the operating system emulation layer is very important. In order to make lwIP portable, operating system specif

35、ic function calls and data structures are not used directly in the code. Instead, when such functions are needed the operating system emulation layer is used. The operating s</p><p>　　Besides, we have to put

36、 attention on two questions about Formula during the implementation of lwIP[6].</p><p>　　1) Message</p><p>　　We can't use the messages which in the message queue directly, because Formula do

37、esn't manage them. We must implement them based on the Formula. The structure defined to manage the messages.</p><p>　　typedef struct{</p><p>　　OS_EVENT * pQ;</p><p>　　void * pv

38、QEntries[MAX_ QUEUE_ ENTRIES];</p><p>　　􀀃}stack_mbox_t;</p><p>　　To the queue itself managed by Formula and use the module of EMS memory manage to realize the set, use and delete of mes

39、sage. The integration of the above two can form the message queue function of lwIP</p><p>　　2) Create New Thread</p><p>　　There is no thread but task in Formula We can create the new thread thro

40、ugh calling OSTaskCreate (), but we must assigned the PRI for the new thread in lwIP in advance.</p><p>　　IVREALIZATION OF EWS</p><p>　　The porting of lwIP is the key to realize the EWS[7]. The

41、 server based on lwIP we named thin server[8], it satisfies the embedded devices' request. The device information can be uploaded on the web page and appear as data, table and cartoon etc. Embedded web server issue t

42、he data to the Internet as the web page so that the remote user can browse the information. From the web page we can know the detailed status of devices and make the relevant control immediately. In application layer, HT

43、TP is t</p><p>　　VAPPLICATION AND TEST OF EWS</p><p>　　Using PING command to link EWS in local area network, we can get four response data packages and the time it used is less than 20ms and th

44、ere is no data package lost. This EWS was tested on the Production of Storage Battery Control System which belongs to Tuo-Chi Electric Appliance Company in Zi-Bo. When we input the IP address of Production of Storage Bat

45、tery Control System, we can open the web page through the browser quickly and correctly. Thus we can believe the EWS can long-distance monitor</p><p>　　VI CONCLUSION</p><p>　　The advantages of

46、 this EWS are low cost, visualization, platform independent, flexible deployment, excellent remote accessing, etc. The equipments can be monitored and controlled flexibly in web pages through embedded web server. In indu

47、stry control field, the using of embedded web server on intelligence device, instrument and sensor to realize flexible remote control has very high theoretical and application value.</p><p>　　REFERENCES</

48、p><p>　　1. Bilek J, Ruzicka IP. Evolutionary trends of embedded systems. IEEE International Conference on Industrial Technology, vol 2, no 3, 2003, pp. 901-905.</p><p>　　2. Adam D. Design and Imple

49、mentation of the LwIP TCP / IP Stack[Z]. Swedish Institute of Computer Science, 2001.</p><p>　　3. Tian Ze. The Development and Implementation of Embedded System [M].Beijing: Bei Hang University Press, 2005.&

50、lt;/p><p>　　4. Jean J. Labrosse. The Embedded Real-time μC/OS-II [M]. Beijing: Bei Hang University Press, 2003.</p><p>　　5. J. Benthem. TCP/IP Lean: Embedded WEB Server [M]. Beijing: China Machine

51、Press, 2003.</p><p>　　6. Yang Ye. The Implementation of TCP/IP under μC/OS-II [J]. Microcontrollers & Embedded Systems, vol 7, no 3, 2003, pp. 80-83</p><p>　　7. Ju H T, Choi M J, Hong J W. &

52、quot;Ews-based management application interface and integration mechanisms for web-based element management," Journal of Network and Systems Management, vol.9, no. 1, pp. 31-50., Jan, 2001.</p><p>　　8.

53、Xu Feng, Chen Yan, Zhao Hai, Han Guang-jie. Study on Architecture of Internet Access Server for Non-PC Devices [J]. Journal of Northeastern University (Natural Science), vol 26, no 1, 2005, pp. 236-239.</p><p&

54、gt;　　9. Gao Po-po, Shao Shi. Research and Implementation of Embedded Web Server on Low-end Device[J]. Computer Engineering, vol 31, no 5, 2005, pp. 219-221.</p><p><b>　　譯文：</b></p><p&g

55、t;　　嵌入式Web服務(wù)器輕量級(jí)TCP/IP的移植與實(shí)現(xiàn)</p><p>　　摘要 - 嵌入式技術(shù)的發(fā)展需要網(wǎng)絡(luò)/服務(wù)器技術(shù)在嵌入式領(lǐng)域的應(yīng)用，并提供基于互聯(lián)網(wǎng)瀏覽器的遠(yuǎn)程設(shè)備監(jiān)控和管理功能。但是，由于硬件資源有限和通用TCP / IP協(xié)議棧、協(xié)議模型的低效率，在嵌入式系統(tǒng)接入到因特網(wǎng)時(shí)實(shí)現(xiàn)完整的TCP/ IP協(xié)議是非常困難的。本文分析了輕量級(jí)TCP / IP協(xié)議，并給出協(xié)議每一層的詳細(xì)處理，再基于飛利浦LPC2

56、200與RTL8019AS設(shè)計(jì)硬件平臺(tái)與UC/ OS-II核心軟件平臺(tái)，在以上基礎(chǔ)上進(jìn)行LwIP的移植。輕型服務(wù)器是基于LwIP設(shè)計(jì)的，并且能分析通信時(shí)客戶(hù)端和服務(wù)器狀態(tài)的轉(zhuǎn)換。最后，EWS被用于對(duì)蓄電池生產(chǎn)控制系統(tǒng)的測(cè)試，結(jié)果表明該EWS可實(shí)時(shí)并很好地進(jìn)行遠(yuǎn)程監(jiān)控設(shè)備。 </p><p>　　關(guān)鍵詞 - LwIP;嵌入式技術(shù);網(wǎng)頁(yè)服務(wù)器; uC / OS-II;</p><p><

57、b>　　一． 簡(jiǎn)介：</b></p><p>　　傳統(tǒng)的互聯(lián)網(wǎng)網(wǎng)頁(yè)服務(wù)器是胖服務(wù)器/瘦客戶(hù)機(jī)模式，當(dāng)傳送和存儲(chǔ)大量的數(shù)據(jù)時(shí)，這個(gè)模式是完美的，但在嵌入式領(lǐng)域它的表現(xiàn)并不優(yōu)異。互聯(lián)網(wǎng)已經(jīng)成為世界上最重要的基礎(chǔ)信息設(shè)施之一，WWW提供服務(wù)已成為增長(zhǎng)最快并廣泛應(yīng)用的服務(wù)之一，它在可視化，遠(yuǎn)程訪(fǎng)問(wèn)，多數(shù)據(jù)格式支持，平臺(tái)客戶(hù)端的獨(dú)立和使客戶(hù)端變瘦等方面具有很大優(yōu)勢(shì)。嵌入式設(shè)備通過(guò)連接到互聯(lián)網(wǎng)，可以很好地實(shí)

58、現(xiàn)Web服務(wù)，從而實(shí)現(xiàn)通過(guò)瀏覽器靈活地進(jìn)行遠(yuǎn)程監(jiān)控和管理，這已經(jīng)成為嵌入式技術(shù)發(fā)展的一個(gè)必然趨勢(shì)[1]。 </p><p>　　但是，由于硬件資源有限和通用TCP / IP協(xié)議棧、協(xié)議模型的低效率，在嵌入式系統(tǒng)接入到網(wǎng)絡(luò)時(shí)實(shí)現(xiàn)完整的TCP/ IP協(xié)議是非常難的。因此，我們需要移植TCP / IP子網(wǎng)到嵌入式系統(tǒng)中。為了保證實(shí)時(shí)性和可靠性，我們還需要移植</p><p>　　μC/ OS-I

59、I。考慮到時(shí)間和性能的限制，最好是使用裁剪的TCP / IP。 </p><p>　　LWIP[2]（Light-Weight Internet Protocol）是一個(gè)獨(dú)立實(shí)現(xiàn)的小型TCP / IP協(xié)議套件，由Adam Dunkels在瑞典計(jì)算機(jī)科學(xué)院（SICS）的計(jì)算機(jī)和網(wǎng)絡(luò)架構(gòu)（CNA）實(shí)驗(yàn)室開(kāi)發(fā)。lwIP協(xié)議棧實(shí)現(xiàn)的重點(diǎn)是在減少內(nèi)存使用量和代碼尺寸的情況下，使LWIP適用于資源非常有限的小型客戶(hù)端。 &l

60、t;/p><p><b>　　LWIP的特點(diǎn)： </b></p><p>　　- IP（Internet Protocol）包括通過(guò)多個(gè)網(wǎng)絡(luò)接口的數(shù)據(jù)包轉(zhuǎn)發(fā) </p><p>　　- ICMP（Internet Control Message Protocol）用于網(wǎng)絡(luò)維護(hù)和調(diào)試 </p><p>　　- UDP（User

61、Datagram Protocol）包括實(shí)驗(yàn)UDP-lite的擴(kuò)展 </p><p>　　- TCP（Transmission Control Protocol）擁有擁塞控制，RTT估算和快速恢復(fù)/快速重傳 </p><p>　　- 專(zhuān)業(yè)的原API性能增強(qiáng)</p><p>　　- 可選Berkeley-alike套接字API </p><p>

62、;　　- DHCP（Dynamic Host Configuration Protocol） </p><p>　　- PPP（Point-to-Point Protocol） </p><p>　　- ARP（Address Resolution Protocol）用于以太網(wǎng)</p><p><b>　　二． 分析：</b></p>

63、;<p><b>　　A. IP處理</b></p><p>　　LwIP只實(shí)現(xiàn)了IP最基本的功能。它可以發(fā)送，接收和轉(zhuǎn)發(fā)數(shù)據(jù)包，但不能發(fā)送或接收IP數(shù)據(jù)包碎片，也不處理數(shù)據(jù)包的IP選項(xiàng)。對(duì)于大多數(shù)應(yīng)用程序，這并不構(gòu)成任何問(wèn)題。</p><p><b>　　1）接收數(shù)據(jù)包</b></p><p>　　對(duì)于傳入

64、的IP數(shù)據(jù)包，當(dāng)ip_input()函數(shù)被一個(gè)網(wǎng)絡(luò)設(shè)備驅(qū)動(dòng)程序調(diào)用時(shí)，處理開(kāi)始。在這里，完成IP版本字段和報(bào)頭長(zhǎng)度的初始檢查，并對(duì)包頭校驗(yàn)和進(jìn)行計(jì)算校驗(yàn)。接下來(lái)，這個(gè)函數(shù)檢查目的地址與網(wǎng)絡(luò)接口的IP地址，來(lái)確定數(shù)據(jù)包的目的地是否為主機(jī)。</p><p><b>　　2）發(fā)送數(shù)據(jù)包</b></p><p>　　發(fā)送的數(shù)據(jù)包由ip_output()處理，它通過(guò)ip_rou

65、te()找到合適的網(wǎng)絡(luò)接口來(lái)傳輸數(shù)據(jù)包。當(dāng)輸出網(wǎng)絡(luò)接口是確定的，該數(shù)據(jù)包被傳遞到ip_output_if()，這個(gè)函數(shù)把輸出的網(wǎng)絡(luò)接口作為一個(gè)參數(shù)。在這里，所有IP報(bào)頭域被填充并完成IP報(bào)頭校驗(yàn)和計(jì)算。IP數(shù)據(jù)包的源地址和目的地址被作為一個(gè)參數(shù)傳遞給函數(shù)ip_output_if()。</p><p><b>　　B. ICMP處理</b></p><p>　　ip_i

66、nput()接收的ICMP數(shù)據(jù)包由icmp_input()進(jìn)行解碼，并進(jìn)行適當(dāng)處理。ICMP目的地址不可達(dá)消息可以通過(guò)傳輸層協(xié)議發(fā)送，特別是通過(guò)UDP，函數(shù)icmp_dest_unreach()就是用來(lái)發(fā)送此類(lèi)信息的。對(duì)于ICMP的處理如圖1所示。</p><p><b>　　C. UDP處理</b></p><p>　　UDP是一個(gè)簡(jiǎn)單的協(xié)議，用于在不同的過(guò)程之間解

67、析復(fù)用數(shù)據(jù)包。每個(gè)UDP會(huì)話(huà)狀態(tài)保存在一個(gè)PCB結(jié)構(gòu)中。當(dāng)由PCB指定會(huì)話(huà)的一個(gè)數(shù)據(jù)包被接收時(shí)，最后兩個(gè)參數(shù)recv和recv_arg將被使用。當(dāng)數(shù)據(jù)包被接收時(shí)，recv所指向的函數(shù)將被被調(diào)用。</p><p>　　由于UDP的簡(jiǎn)單性，輸入和輸出的處理也同樣簡(jiǎn)單，并遵循一個(gè)相當(dāng)直的線(xiàn)（圖2）。發(fā)送數(shù)據(jù)時(shí)，應(yīng)用程序調(diào)用udp_send（），而udp_send（）將調(diào)用udp_output（）。在這里，將完成必要的校

68、驗(yàn)求和，填充UDP報(bào)頭的字段。因?yàn)樾ｒ?yàn)和包括該IP包的IP源地址，函數(shù)ip_route（）在某些情況下被調(diào)用，以便查找發(fā)送數(shù)據(jù)包的網(wǎng)絡(luò)接口。該網(wǎng)絡(luò)接口的IP地址將作為發(fā)送數(shù)據(jù)包的源IP地址。最后，該包被移交給ip_ output_if（）進(jìn)行傳輸。</p><p><b>　　D. TCP處理 </b></p><p>　　TCP是傳輸層協(xié)議，它為應(yīng)用層提供了可靠的字

69、節(jié)流服務(wù)。 </p><p>　　基本的TCP處理（圖3）分為六大函數(shù);當(dāng)一個(gè)應(yīng)用程序需要發(fā)送TCP數(shù)據(jù)時(shí)，tcp_write（）被調(diào)用。函數(shù)tcp_write（）通過(guò)調(diào)用tcp_enqueue（）將數(shù)據(jù)轉(zhuǎn)換成大小合適的TCP段，并把TCP段放至傳輸隊(duì)列。函數(shù)tcp_output（）將檢查是否可以發(fā)送數(shù)據(jù)，當(dāng)ip_input（）驗(yàn)證IP頭后傳送TCP段給函數(shù)tcp_input（）時(shí)，輸入處理開(kāi)始。這個(gè)函數(shù)完成初始

70、完整性檢查，并決定TCP段所屬的TCP連接。TCP段通過(guò)tcp_process（）進(jìn)行處理，此函數(shù)實(shí)現(xiàn)了TCP狀態(tài)機(jī)，以及處理任何必要的狀態(tài)轉(zhuǎn)換。如果在接收網(wǎng)絡(luò)數(shù)據(jù)的狀態(tài)下，函數(shù)tcp_receive（）將被調(diào)用。如果是這樣，tcp_receive（）將推送此段到一個(gè)應(yīng)用程序。如果該段構(gòu)成不可識(shí)別數(shù)據(jù)的ACK，該數(shù)據(jù)將從緩沖區(qū)移除并回收其內(nèi)存。此外，如果收到數(shù)據(jù)的ACK說(shuō)明接收者可能愿意接收更多的數(shù)據(jù)，tcp_output（）將被調(diào)用。

71、</p><p>　　三． 基于UC/OS-II的LwIP移植：</p><p>　　如今UC/OS-II[4]的移植已經(jīng)很容易了，所以我就直接討論LwIP的移植。 </p><p>　　LwIP已經(jīng)把有關(guān)硬件，操作系統(tǒng)，編譯器的部分包含在/ src/arch下。我們的主要任務(wù)是完善文件目錄下的內(nèi)容，并在移植過(guò)程中略微修改其他文件。在這個(gè)移植中，實(shí)現(xiàn)操作系統(tǒng)模擬層是

72、非常重要的。為了使LwIP的具有可移植性，操作系統(tǒng)特定的函數(shù)調(diào)用和數(shù)據(jù)結(jié)構(gòu)是不能直接在代碼中使用。相反，當(dāng)需要這些函數(shù)時(shí)，操作系統(tǒng)模擬層就被使用了。該操作系統(tǒng)模擬層給操作系統(tǒng)服務(wù)提供了統(tǒng)一的接口，如定時(shí)器，進(jìn)程同步和消息傳遞機(jī)制。原則上，當(dāng)移植LwIP到其他操作系統(tǒng)上時(shí)，只有為這個(gè)特定的操作系統(tǒng)實(shí)現(xiàn)操作系統(tǒng)模擬層是必要的。這個(gè)操作系統(tǒng)模擬層為底層操作系統(tǒng)和LwIP提供一個(gè)接口，因此當(dāng)我們移植LwIP到新的目標(biāo)時(shí)，我們只需要在這一層設(shè)計(jì)一

73、些函數(shù)。這些函數(shù)有關(guān)段，消息，超時(shí)，新的線(xiàn)程等。 </p><p>　　此外，在lwIP的實(shí)現(xiàn)過(guò)程中，我們必須注意有關(guān)UC/OS-II的兩個(gè)問(wèn)題[6]。 </p><p><b>　　1）信息 </b></p><p>　　在消息隊(duì)列中，我們不能直接使用的消息，因?yàn)閁C/OS-II并不對(duì)其進(jìn)行管理。我們必須根據(jù)UC/OS-II來(lái)實(shí)現(xiàn)它們。以下結(jié)

74、構(gòu)用來(lái)管理信息。 </p><p>　　typedef struct{</p><p>　　OS_EVENT * pQ;</p><p>　　void * pvQEntries[MAX_ QUEUE_ ENTRIES];</p><p>　　􀀃}stack_mbox_t;</p><p>　　對(duì)于隊(duì)列

75、本身，由UC/OS-II來(lái)管理，并且使用EMS內(nèi)存模塊管理實(shí)現(xiàn)集，使用和刪除的消息。整合上述兩成員就形成了lwIP的消息隊(duì)列功能。 </p><p><b>　　2）創(chuàng)建新線(xiàn)程</b></p><p>　　在UC/OS-II中沒(méi)有線(xiàn)程，只有任務(wù)。我們可以通過(guò)調(diào)用OSTaskCreate（）創(chuàng)建一個(gè)新的線(xiàn)程，但我們必須提前分配優(yōu)先級(jí)給在lwIP中的新線(xiàn)程。 </p

76、><p>　　四． EWS的實(shí)現(xiàn)：</p><p>　　LwIP的移植是實(shí)現(xiàn)EWS的關(guān)鍵[7]?；贚wIP的服務(wù)器我們稱(chēng)為瘦服務(wù)器[8]，其滿(mǎn)足嵌入式設(shè)備的要求。該設(shè)備的信息可以被上傳至網(wǎng)頁(yè)上，并以數(shù)據(jù)，表和動(dòng)畫(huà)等形式顯示。嵌入式Web服務(wù)器將數(shù)據(jù)上傳至網(wǎng)絡(luò)上，并在網(wǎng)頁(yè)上顯示，以便用戶(hù)可以遠(yuǎn)程瀏覽信息。我們可以從網(wǎng)頁(yè)中知道設(shè)備的詳細(xì)狀態(tài)，并立刻進(jìn)行相關(guān)控制。在應(yīng)用層，HTTP是主要的協(xié)議，我

77、們可以監(jiān)視現(xiàn)場(chǎng)設(shè)備或下載最新的驅(qū)動(dòng)程序。此外，在LwIP中的DHCP對(duì)于我們的EMS是非常有利的。這是種典型的網(wǎng)絡(luò)/服務(wù)器服務(wù)模式，主服務(wù)器可以從客戶(hù)端接收請(qǐng)求數(shù)據(jù)包，讀取解析請(qǐng)求消息，并發(fā)送響應(yīng)給客戶(hù)端[9]。EWS的狀態(tài)變換如圖4。在被添加到服務(wù)器中的“RESET”狀態(tài)下，不需要接收任何消息就可以直接跳轉(zhuǎn)到“LISTEN”狀態(tài)。這個(gè)服務(wù)器的端口始終是敞開(kāi)的。當(dāng)連接建立后，一旦服務(wù)器發(fā)現(xiàn)“ACK”包是錯(cuò)誤的，或者服務(wù)器端口不是80，狀

78、態(tài)機(jī)將跳轉(zhuǎn)到“RESET”狀態(tài)并發(fā)送一個(gè)“RST”幀，以重新建立連接。為了避免網(wǎng)絡(luò)阻塞，一旦連接超時(shí)，它將被關(guān)閉。</p><p>　　五. EWS的測(cè)試和應(yīng)用：</p><p>　　使用ping命令在局域網(wǎng)中鏈接EWS，我們可以得到四個(gè)響應(yīng)數(shù)據(jù)包，并且在沒(méi)有丟失任何數(shù)據(jù)包的前提下下耗時(shí)小于20ms，。該EWS已經(jīng)在拓馳電器公司的蓄電池生產(chǎn)控制系統(tǒng)上進(jìn)行測(cè)試過(guò)。當(dāng)我們輸入蓄電池生產(chǎn)控制系統(tǒng)

79、的IP地址時(shí)，我們可以通過(guò)瀏覽器快速，準(zhǔn)確地打開(kāi)寫(xiě)有相關(guān)信息的網(wǎng)頁(yè)。因此，我們可以相信，本EWS可以很好地實(shí)現(xiàn)實(shí)時(shí)、遠(yuǎn)距離地監(jiān)控設(shè)備。功能是分配IP地址。使用HTTP網(wǎng)絡(luò)。 </p><p><b>　　六. 結(jié)論：</b></p><p>　　本EWS的優(yōu)點(diǎn)是成本低，可視化，獨(dú)立的平臺(tái)，靈活的部署，優(yōu)良的遠(yuǎn)程訪(fǎng)問(wèn)功能等。通過(guò)嵌入式Web服務(wù)器，可以在網(wǎng)頁(yè)上對(duì)設(shè)備進(jìn)行

80、監(jiān)測(cè)和靈活地控制。在工業(yè)控制領(lǐng)域中，對(duì)智能設(shè)備、儀器和傳感器使用嵌入式Web服務(wù)器對(duì)于實(shí)現(xiàn)遠(yuǎn)程靈活的控制具有很高的理論意義和應(yīng)用價(jià)值。</p><p><b>　　參考文獻(xiàn)：</b></p><p>　　1. Bilek J, Ruzicka IP. Evolutionary trends of embedded systems. IEEE International

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