Implement "no route to host" error message as described in bug 106188.
More precisely, the current nsSocketTransport.cpp code always reports "Connection refused by peer" when a connection setup failed. But "Connection refused by peer" is just one of the possible reasons. There are also "Connection timed out", "No route to host", etc.
The "connection refused" is reported even if the connection is closed before any data is sent by the server. That is, of course, long after the connection setup. try "netcat -l -p 1234" and in mozila http://127.0.0.1:1234/askdfjhdkfjh and then killing netcat with Ctrl+C or kill -TERM.
pushing this out post 1.0... will pull it in if time permits. -> 1.0.1
mass futuring of untargeted bugs
related: bug 217792
this granularity won't help our users