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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".

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The reason for the error was there was a typo in the Gateway and Subnet Mask network configuration :\

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