看zookpeer的这篇文档 的时候,有如下一段英文:

Ordered delivery
   Data is delivered in the same order it is sent and a message m is delivered only after all messages sent
   before m have been delivered. (The corollary to this is that if message m is lost all messages after m will 
   be lost.)

这段文字讲的是TCP的一个特性,发送的有序性和接收的有序性。以前认为 sentdelivered 这两个词是相同的,但如果是相同的,那么上述这段文字就很难理解了, Data is delivered in the same order it is sent这段话使用了这两个词,如果这两个词意思相同,那么这段话就会变成 Data is sent in the same order it is sent ,这段话就不知道想表达什么。于是我查了下 sentdelivered 的意思,得到了如下的解释:

"Sent" is just that something has been despatched. 例如发送邮件用的就是sent,东西没有直接给对方,而是给了第三方,再由第三方给对方
"Delivered" means that the goods have arrived at their desitnation and have been received.

有了如上的解释,上面的这段话就好理解了。