I work with microprocessor devices that have/run a micro webserver.
I have two of these devices set up so that they can be accessible to/by the Internet - I'll call the devices "A" and "B".
Currently, I can successfully connect to "A" from the Internet (and via its LAN). However, I cannot connect to "B" from the Internet, but I can connect to "B" via its LAN. Note that "B" is not behind a firewall - it is naked to the Internet.
Using Fiddler2 to peek at what's going on, I noticed that when I connect to "A" from the Internet the Request Header reads:
..... **Connection: keep-alive** User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/534.30 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
When I attempt to connect to "B" from the Internet, the Request Header reads: (this connection always fails)
..... **Proxy-Connection: keep-alive** User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/534.30 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
When I connect to "B" from its LAN, the Request Header reads: (this connection always succeeds)
..... **Connection: keep-alive** User-Agent: Mozilla/5.0 (Windows NT 6.0) AppleWebKit/534.30 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
To be clear, in all the different ways I have attempted to connect to the devices "A" and "B", I noticed consistent behavior where all failed connections contain the "Proxy-Connection: keep-alive" header value and all successful connections contain the "Connection: keep-alive" header value.
Also, using Fiddler, I noticed that the server response on a failed connection read:
"No connection could be made because the target machine actively refused it".
