getsockopt

        # BasicSocket.getsockopt

(from ruby core)
---
    getsockopt(level, optname) => socketoption

---

Gets a socket option. These are protocol and system specific, see your
local system documentation for details. The option is returned as a
Socket::Option object.

### Parameters
*   `level` is an integer, usually one of the SOL_ constants such as
    Socket::SOL_SOCKET, or a protocol level. A string or symbol of the
    name, possibly without prefix, is also accepted.
*   `optname` is an integer, usually one of the SO_ constants, such as
    Socket::SO_REUSEADDR. A string or symbol of the name, possibly
    without prefix, is also accepted.


### Examples

Some socket options are integers with boolean values, in this case
#getsockopt could be called like this:

    reuseaddr = sock.getsockopt(:SOCKET, :REUSEADDR).bool

    optval = sock.getsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR)
    optval = optval.unpack "i"
    reuseaddr = optval[0] == 0 ? false : true

Some socket options are integers with numeric values, in this case
#getsockopt could be called like this:

    ipttl = sock.getsockopt(:IP, :TTL).int

    optval = sock.getsockopt(Socket::IPPROTO_IP, Socket::IP_TTL)
    ipttl = optval.unpack1("i")

Option values may be structs. Decoding them can be complex as it
involves examining your system headers to determine the correct
definition. An example is a +struct linger+, which may be defined in
your system headers as:
    struct linger {
      int l_onoff;
      int l_linger;
    };

In this case #getsockopt could be called like this:

    # Socket::Option knows linger structure.
    onoff, linger = sock.getsockopt(:SOCKET, :LINGER).linger

    optval =  sock.getsockopt(Socket::SOL_SOCKET, Socket::SO_LINGER)
    onoff, linger = optval.unpack "ii"
    onoff = onoff == 0 ? false : true