getsockopt

Gets a socket option. These are protocol and system specific, see your local sytem documentation for details. The option is returned as a String with the data being the binary value of the socket option.

Parameters

• level is an integer, usually one of the SOL_ constants such as

Socket::SOL_SOCKET, or a protocol level.

• optname is an integer, usually one of the SO_ constants, such

as Socket::SO_REUSEADDR.

Examples

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

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:

optval = sock.getsockopt(Socket::IPPROTO_IP, Socket::IP_TTL)
ipttl = optval.unpack("i")[0]

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:

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