Method: BasicSocket#getsockopt

Defined in:

basicsocket.c

#getsockopt(level, optname) ⇒ Object

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.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:

# 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

# File 'basicsocket.c', line 305

static VALUE
bsock_getsockopt(VALUE sock, VALUE lev, VALUE optname)
{
    int level, option;
    socklen_t len;
    char *buf;
    rb_io_t *fptr;
    int family;

    GetOpenFile(sock, fptr);
    family = rsock_getfamily(fptr->fd);
    level = rsock_level_arg(family, lev);
    option = rsock_optname_arg(family, level, optname);
    len = 256;
    buf = ALLOCA_N(char,len);

    rb_io_check_closed(fptr);

    if (getsockopt(fptr->fd, level, option, buf, &len) < 0)
  rsock_sys_fail_path("getsockopt(2)", fptr->pathv);

    return rsock_sockopt_new(family, level, option, rb_str_new(buf, len));
}