系統(tǒng)首先要完成一系列必要的初始化，包括協(xié)議棧和設(shè)備的初始化。對DNS的初始化主要包括：一，創(chuàng)建DNS服務(wù)器鏈表（服務(wù)器鏈表的大小可以根據(jù)實際需要開辟，本設(shè)計中使用5個），此時該鏈表是空的；二，創(chuàng)建DNS主機(jī)緩存，可以將一些常用的域名與IP映射信息存放在緩存中，供終端設(shè)備直接查找。
當(dāng)完成上述的初始化以后，接下來進(jìn)行PPP撥號，向運(yùn)營商的服務(wù)中心發(fā)送LCP、NCP連接配置請求的數(shù)據(jù)包。其中NCP向服務(wù)中心發(fā)送請求分配DNS解析服務(wù)器的配置請求數(shù)據(jù)包，根據(jù)NCP的幀格式進(jìn)行封裝。代碼實現(xiàn)的流程如圖2所示。
3．2 域名解析的實現(xiàn)
最終WDTU連接到登錄花生殼客戶端的主機(jī)，與之實現(xiàn)數(shù)據(jù)傳輸。花生殼客戶端會將登錄主機(jī)的IP與申請的該域名的映射信息返回給花生殼公司的DNS服務(wù)器。而運(yùn)營商與這些提供域名解析服務(wù)的公司之間建立聯(lián)系，提供DNS服務(wù)的公司通過直接或間接的連接，將本公司的DNS服務(wù)器域名信息系統(tǒng)與運(yùn)營商的服務(wù)中心相連接，這樣，運(yùn)營商就使得移動終端實現(xiàn)了域名的解析。DNS功能有多種類型，但主要的是兩種：由域名得到IP地址和根據(jù)IP地址得到相映射的域名。實際應(yīng)用中主要是需要根據(jù)域名查找到與之相對應(yīng)的IP地址。因此，本設(shè)計也是針對這種類型介紹的。
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