BasicSocket

Class

BasicSocket is the super class for all the Socket classes.

Class Methods

BasicSocket.do_not_reverse_lookup => true or false
::

Gets the global do_not_reverse_lookup flag.

BasicSocket.do_not_reverse_lookup  #=> false

BasicSocket.do_not_reverse_lookup = bool
::

Sets the global do_not_reverse_lookup flag.

The flag is used for initial value of do_not_reverse_lookup for each socket.

s1 = TCPSocket.new("localhost", 80)
p s1.do_not_reverse_lookup                 #=> true
BasicSocket.do_not_reverse_lookup = false
s2 = TCPSocket.new("localhost", 80)
p s2.do_not_reverse_lookup                 #=> false
p s1.do_not_reverse_lookup                 #=> true

BasicSocket.for_fd(fd) => basicsocket
::

Returns a socket object which contains the file descriptor, fd.

# If invoked by inetd, STDIN/STDOUT/STDERR is a socket.
STDIN_SOCK = Socket.for_fd(STDIN.fileno)
p STDIN_SOCK.remote_address
Instance Methods

basicsocket.close_read => nil
#

Disallows further read using shutdown system call.

s1, s2 = UNIXSocket.pair
s1.close_read
s2.puts #=> Broken pipe (Errno::EPIPE)

basicsocket.close_write => nil
#

Disallows further write using shutdown system call.

UNIXSocket.pair {|s1, s2|
  s1.print "ping"
  s1.close_write
  p s2.read        #=> "ping"
  s2.print "pong"
  s2.close
  p s1.read        #=> "pong"
}

connect_address
#

Returns an address of the socket suitable for connect in the local machine.

This method returns self.local_address, except following condition.

  • IPv4 unspecified address (0.0.0.0) is replaced by IPv4 loopback address (127.0.0.1).

  • IPv6 unspecified address (::) is replaced by IPv6 loopback address (::1).

If the local address is not suitable for connect, SocketError is raised. IPv4 and IPv6 address which port is 0 is not suitable for connect. Unix domain socket which has no path is not suitable for connect.

Addrinfo.tcp("0.0.0.0", 0).listen {|serv|
  p serv.connect_address #=> #<Addrinfo: 127.0.0.1:53660 TCP>
  serv.connect_address.connect {|c|
    s, _ = serv.accept
    p [c, s] #=> [#<Socket:fd 4>, #<Socket:fd 6>]
  }
}

basicsocket.do_not_reverse_lookup => true or false
#

Gets the do_not_reverse_lookup flag of basicsocket.

require 'socket'

BasicSocket.do_not_reverse_lookup = false
TCPSocket.open("www.ruby-lang.org", 80) {|sock|
  p sock.do_not_reverse_lookup      #=> false
}
BasicSocket.do_not_reverse_lookup = true
TCPSocket.open("www.ruby-lang.org", 80) {|sock|
  p sock.do_not_reverse_lookup      #=> true
}

basicsocket.do_not_reverse_lookup = bool
#

Sets the do_not_reverse_lookup flag of basicsocket.

TCPSocket.open("www.ruby-lang.org", 80) {|sock|
  p sock.do_not_reverse_lookup       #=> true
  p sock.peeraddr                    #=> ["AF_INET", 80, "221.186.184.68", "221.186.184.68"]
  sock.do_not_reverse_lookup = false
  p sock.peeraddr                    #=> ["AF_INET", 80, "carbon.ruby-lang.org", "54.163.249.195"]
}

basicsocket.getpeereid => [euid, egid]
#

Returns the user and group on the peer of the UNIX socket. The result is a two element array which contains the effective uid and the effective gid.

Socket.unix_server_loop("/tmp/sock") {|s|
  begin
    euid, egid = s.getpeereid

    # Check the connected client is myself or not.
    next if euid != Process.uid

    # do something about my resource.

  ensure
    s.close
  end
}

basicsocket.getpeername => sockaddr
#

Returns the remote address of the socket as a sockaddr string.

TCPServer.open("127.0.0.1", 1440) {|serv|
  c = TCPSocket.new("127.0.0.1", 1440)
  s = serv.accept
  p s.getpeername #=> "\x02\x00\x82u\x7F\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00"
}

If Addrinfo object is preferred over the binary string, use BasicSocket#remote_address.

basicsocket.getsockname => sockaddr
#

Returns the local address of the socket as a sockaddr string.

TCPServer.open("127.0.0.1", 15120) {|serv|
  p serv.getsockname #=> "\x02\x00;\x10\x7F\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00"
}

If Addrinfo object is preferred over the binary string, use BasicSocket#local_address.

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.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

bsock.local_address => addrinfo
#

Returns an Addrinfo object for local address obtained by getsockname.

Note that addrinfo.protocol is filled by 0.

TCPSocket.open("www.ruby-lang.org", 80) {|s|
  p s.local_address #=> #<Addrinfo: 192.168.0.129:36873 TCP>
}

TCPServer.open("127.0.0.1", 1512) {|serv|
  p serv.local_address #=> #<Addrinfo: 127.0.0.1:1512 TCP>
}

basicsocket.recv(maxlen[, flags[, outbuf]]) => mesg
#

Receives a message.

maxlen is the maximum number of bytes to receive.

flags should be a bitwise OR of Socket::MSG_* constants.

outbuf will contain only the received data after the method call even if it is not empty at the beginning.

UNIXSocket.pair {|s1, s2|
  s1.puts "Hello World"
  p s2.recv(4)                     #=> "Hell"
  p s2.recv(4, Socket::MSG_PEEK)   #=> "o Wo"
  p s2.recv(4)                     #=> "o Wo"
  p s2.recv(10)                    #=> "rld\n"
}

basicsocket.recv_nonblock(maxlen [, flags [, buf [, options ]]]) => mesg
#

Receives up to maxlen bytes from socket using recvfrom(2) after O_NONBLOCK is set for the underlying file descriptor. flags is zero or more of the MSG_ options. The result, mesg, is the data received.

When recvfrom(2) returns 0, Socket#recv_nonblock returns an empty string as data. The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.

Parameters

  • maxlen - the number of bytes to receive from the socket

  • flags - zero or more of the MSG_ options

  • buf - destination String buffer

  • options - keyword hash, supporting ‘exception: false`

Example 

serv = TCPServer.new("127.0.0.1", 0)
af, port, host, addr = serv.addr
c = TCPSocket.new(addr, port)
s = serv.accept
c.send "aaa", 0
begin # emulate blocking recv.
  p s.recv_nonblock(10) #=> "aaa"
rescue IO::WaitReadable
  IO.select([s])
  retry
end

Refer to Socket#recvfrom for the exceptions that may be thrown if the call to recv_nonblock fails.

BasicSocket#recv_nonblock may raise any error corresponding to recvfrom(2) failure, including Errno::EWOULDBLOCK.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by IO::WaitReadable. So IO::WaitReadable can be used to rescue the exceptions for retrying recv_nonblock.

By specifying a keyword argument exception to false, you can indicate that recv_nonblock should not raise an IO::WaitReadable exception, but return the symbol :wait_readable instead.

See

basicsocket.recvmsg(maxmesglen=nil, flags=0, maxcontrollen=nil, opts={}) => [mesg, sender_addrinfo, rflags, *controls]
#

recvmsg receives a message using recvmsg(2) system call in blocking manner.

maxmesglen is the maximum length of mesg to receive.

flags is bitwise OR of MSG_* constants such as Socket::MSG_PEEK.

maxcontrollen is the maximum length of controls (ancillary data) to receive.

opts is option hash. Currently :scm_rights=>bool is the only option.

:scm_rights option specifies that application expects SCM_RIGHTS control message. If the value is nil or false, application don’t expects SCM_RIGHTS control message. In this case, recvmsg closes the passed file descriptors immediately. This is the default behavior.

If :scm_rights value is neither nil nor false, application expects SCM_RIGHTS control message. In this case, recvmsg creates IO objects for each file descriptors for Socket::AncillaryData#unix_rights method.

The return value is 4-elements array.

mesg is a string of the received message.

sender_addrinfo is a sender socket address for connection-less socket. It is an Addrinfo object. For connection-oriented socket such as TCP, sender_addrinfo is platform dependent.

rflags is a flags on the received message which is bitwise OR of MSG_* constants such as Socket::MSG_TRUNC. It will be nil if the system uses 4.3BSD style old recvmsg system call.

controls is ancillary data which is an array of Socket::AncillaryData objects such as:

#<Socket::AncillaryData: AF_UNIX SOCKET RIGHTS 7>

maxmesglen and maxcontrollen can be nil. In that case, the buffer will be grown until the message is not truncated. Internally, MSG_PEEK is used. Buffer full and MSG_CTRUNC are checked for truncation.

recvmsg can be used to implement recv_io as follows:

mesg, sender_sockaddr, rflags, *controls = sock.recvmsg(:scm_rights=>true)
controls.each {|ancdata|
  if ancdata.cmsg_is?(:SOCKET, :RIGHTS)
    return ancdata.unix_rights[0]
  end
}

basicsocket.recvmsg_nonblock(maxdatalen=nil, flags=0, maxcontrollen=nil, opts={}) => [data, sender_addrinfo, rflags, *controls]
#

recvmsg receives a message using recvmsg(2) system call in non-blocking manner.

It is similar to BasicSocket#recvmsg but non-blocking flag is set before the system call and it doesn’t retry the system call.

By specifying a keyword argument exception to false, you can indicate that recvmsg_nonblock should not raise an IO::WaitReadable exception, but return the symbol :wait_readable instead.

bsock.remote_address => addrinfo
#

Returns an Addrinfo object for remote address obtained by getpeername.

Note that addrinfo.protocol is filled by 0.

TCPSocket.open("www.ruby-lang.org", 80) {|s|
  p s.remote_address #=> #<Addrinfo: 221.186.184.68:80 TCP>
}

TCPServer.open("127.0.0.1", 1728) {|serv|
  c = TCPSocket.new("127.0.0.1", 1728)
  s = serv.accept
  p s.remote_address #=> #<Addrinfo: 127.0.0.1:36504 TCP>
}

basicsocket.send(mesg, flags [, dest_sockaddr]) => numbytes_sent
#

send mesg via basicsocket.

mesg should be a string.

flags should be a bitwise OR of Socket::MSG_* constants.

dest_sockaddr should be a packed sockaddr string or an addrinfo.

TCPSocket.open("localhost", 80) {|s|
  s.send "GET / HTTP/1.0\r\n\r\n", 0
  p s.read
}

basicsocket.sendmsg(mesg, flags=0, dest_sockaddr=nil, *controls) => numbytes_sent
#

sendmsg sends a message using sendmsg(2) system call in blocking manner.

mesg is a string to send.

flags is bitwise OR of MSG_* constants such as Socket::MSG_OOB.

dest_sockaddr is a destination socket address for connection-less socket. It should be a sockaddr such as a result of Socket.sockaddr_in. An Addrinfo object can be used too.

controls is a list of ancillary data. The element of controls should be Socket::AncillaryData or 3-elements array. The 3-element array should contains cmsg_level, cmsg_type and data.

The return value, numbytes_sent is an integer which is the number of bytes sent.

sendmsg can be used to implement send_io as follows:

# use Socket::AncillaryData.
ancdata = Socket::AncillaryData.int(:UNIX, :SOCKET, :RIGHTS, io.fileno)
sock.sendmsg("a", 0, nil, ancdata)

# use 3-element array.
ancdata = [:SOCKET, :RIGHTS, [io.fileno].pack("i!")]
sock.sendmsg("\0", 0, nil, ancdata)

basicsocket.sendmsg_nonblock(mesg, flags=0, dest_sockaddr=nil, *controls, opts={}) => numbytes_sent
#

sendmsg_nonblock sends a message using sendmsg(2) system call in non-blocking manner.

It is similar to BasicSocket#sendmsg but the non-blocking flag is set before the system call and it doesn’t retry the system call.

By specifying a keyword argument exception to false, you can indicate that sendmsg_nonblock should not raise an IO::WaitWritable exception, but return the symbol :wait_writable instead.

setsockopt(level, optname, optval)

setsockopt(socketoption)
#

Sets a socket option. These are protocol and system specific, see your local system documentation for details.

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.

  • optval is the value of the option, it is passed to the underlying setsockopt() as a pointer to a certain number of bytes. How this is done depends on the type:

    • Integer: value is assigned to an int, and a pointer to the int is passed, with length of sizeof(int).

    • true or false: 1 or 0 (respectively) is assigned to an int, and the int is passed as for an Integer. Note that false must be passed, not nil.

    • String: the string’s data and length is passed to the socket.

  • socketoption is an instance of Socket::Option

Examples

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

sock.setsockopt(:SOCKET, :REUSEADDR, true)
sock.setsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR, true)
sock.setsockopt(Socket::Option.bool(:INET, :SOCKET, :REUSEADDR, true))

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

sock.setsockopt(:IP, :TTL, 255)
sock.setsockopt(Socket::IPPROTO_IP, Socket::IP_TTL, 255)
sock.setsockopt(Socket::Option.int(:INET, :IP, :TTL, 255))

Option values may be structs. Passing them can be complex as it involves examining your system headers to determine the correct definition. An example is an ip_mreq, which may be defined in your system headers as:

struct ip_mreq {
  struct  in_addr imr_multiaddr;
  struct  in_addr imr_interface;
};

In this case setsockopt could be called like this:

optval = IPAddr.new("224.0.0.251").hton +
         IPAddr.new(Socket::INADDR_ANY, Socket::AF_INET).hton
sock.setsockopt(Socket::IPPROTO_IP, Socket::IP_ADD_MEMBERSHIP, optval)

basicsocket.shutdown([how]) => 0
#

Calls shutdown(2) system call.

s.shutdown(Socket::SHUT_RD) disallows further read.

s.shutdown(Socket::SHUT_WR) disallows further write.

s.shutdown(Socket::SHUT_RDWR) disallows further read and write.

how can be symbol or string:

  • :RD, :SHUT_RD, “RD” and “SHUT_RD” are accepted as Socket::SHUT_RD.

  • :WR, :SHUT_WR, “WR” and “SHUT_WR” are accepted as Socket::SHUT_WR.

  • :RDWR, :SHUT_RDWR, “RDWR” and “SHUT_RDWR” are accepted as Socket::SHUT_RDWR.

    UNIXSocket.pair {|s1, s2|

    s1.puts "ping"
s1.shutdown(:WR)
p s2.read          #=> "ping\n"
s2.puts "pong"
s2.close
p s1.read          #=> "pong\n"

    }