[Live-devel] Suggestion: replace hard-coded errno values with symbolic constants in readSocket()

[Николай Исаев]

Hello LIVE555 developers,

While debugging an issue on a Cygwin/Windows build of LIVE555, I noticed
that readSocket() in groupsock/GroupsockHelper.cpp uses hard-coded Linux
errno values:

if (err == 111 /*ECONNREFUSED (Linux)*/
...
    || err == 113 /*EHOSTUNREACH (Linux)*/) {
    return 0;
}

Using numeric errno values appears to be fragile across platforms.

On my Cygwin build, I observed:

err = 113
strerror(err) = "Software caused connection abort"
EHOSTUNREACH = 118

As a result, the code treats errno 113 as if it were Linux EHOSTUNREACH,
even though on this platform it represents a different condition. This
caused readSocket() to return 0 instead of propagating the socket error,
leading to a connection that remained active indefinitely.

Would it make sense to replace the hard-coded values with symbolic
constants, e.g.:

if (err == ECONNREFUSED
#if defined(__WIN32__) || defined(_WIN32)
    || err == 0 || err == EWOULDBLOCK
#else
    || err == EAGAIN
#endif
    || err == EHOSTUNREACH) {
    return 0;
}

This would avoid assumptions about platform-specific errno numbering and
prevent accidental matches when errno values differ from Linux.

Best regards,
Nikolay Isaev
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