> in GNU/Linux "system timeout has been reached" -- means that  system timeout will *never* reached.

That's quite likely because the system limits may be very large. For example, on my OSX box:

    --- ~ » sysctl net.inet.tcp.keepinit
    net.inet.tcp.keepinit: 75000

According to Apple developer docs, this is in seconds. Meaning for your example to run all 100 iterations, you'd be looking at an inordinate amount of time to finish a loop that timed out at each connection attempt and deferred to system defaults for the timeout value. Not exactly "never", but far from a reasonable time frame. Of course, this can be tuned to a more reasonable limit.