HTTP断点续传的基本原理

http://127.0.0.3/
S 01-7-12 19:19:40 User-Agent: Mozilla/4.04 [en] (Win95; I ;Nav)
S 01-7-12 19:19:40 Range: bytes=5275648-
S 01-7-12 19:19:40
R 01-7-12 19:19:40 HTTP/1.1 206 Partial Content
R 01-7-12 19:19:40 Server: Zero Http Server/1.0
R 01-7-12 19:19:40 Date: Thu, 12 Jul 2001 11:19:40 GMT
R 01-7-12 19:19:40 Cache-Control: no-cache
R 01-7-12 19:19:40 Last-Modified: Tue, 30 Jan 2001 13:11:30 GMT
R 01-7-12 19:19:40 Content-Type: application/octet-stream
R 01-7-12 19:19:40 Content-Range: bytes 5275648-15143085/15143086
R 01-7-12 19:19:40 Content-Length: 9867438
R 01-7-12 19:19:40 Connection: close
R 01-7-12 19:19:40
P 01-7-12 19:19:40 Data transfer started
I 01-7-12 19:19:41 Job Stopped by user
I 01-7-12 19:19:41 Received 1 124 756 bytes in 0:00:01 (969 617 bytes/s)

第一次是普通的传输；第二次由于没有传完全，就发出了Range这个头部，从5275648字节开始传输（默认是按字节算），回应使用206状态值，表示现在开始部分传输，回复Content-Length头部，表示传输的部分，用字节记，然后就与普通传输没有区别了。