# class Socket

- Socket
- IO
- Reference
- Object

##
Included Modules

- Crystal::System::Socket
- IO::Buffered

##
Direct Known Subclasses

- IPSocket
- UNIXSocket

##
Defined in:

socket.cr
socket/address.cr
socket/addrinfo.cr
socket/common.cr
socket/server.cr

##
Constructors

- .new(family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false)
- .new(fd, family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false)

  Creates a Socket from an existing socket file descriptor / handle.

- .tcp(family : Family, blocking = false) : self

  Creates a TCP socket.

- .unix(type : Type = Type::STREAM, blocking = false) : self

  Creates an UNIX socket.

##
Class Method Summary

- .fcntl(fd, cmd, arg = 0)
- .ip?(string : String)

  Returns `true` if the string represents a valid IPv4 or IPv6 address.

  DEPRECATED Use `IPAddress.valid?` instead

- .udp(family : Family, blocking = false)

  Creates an UDP socket.

##
Instance Method Summary

- #accept : Socket

  Accepts an incoming connection.

- #accept? : Socket | Nil

  Accepts an incoming connection.

- #bind(host : String, port : Int) : Nil

  Binds the socket to a local address.

- #bind(port : Int)

  Binds the socket on port to all local interfaces.

- #bind(addr : Socket::Address) : Nil

  Binds the socket to a local address.

- #blocking
- #blocking=(value)
- #broadcast=(val : Bool)
- #broadcast? : Bool
- #close_on_exec=(arg : Bool)
- #close_on_exec?
- #close_read

  Calls `shutdown(2)` with `SHUT_RD`

- #close_write

  Calls `shutdown(2)` with `SHUT_WR`

- #closed? : Bool

  Returns `true` if this `IO` is closed.

- #connect(host : String, port : Int, connect_timeout = nil) : Nil

  Connects the socket to a remote host:port.

- #connect(addr, timeout = nil) : Nil

  Connects the socket to a remote address.

- #connect(addr, timeout = nil, &)

  Tries to connect to a remote address.

- #family : Family
- #fcntl(cmd, arg = 0)
- #fd

  Returns the handle associated with this socket from the operating system.

- #finalize
- #inspect(io : IO) : Nil

  Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

- #keepalive=(val : Bool)
- #keepalive?
- #linger
- #linger=(val : Int | Nil)

  WARNING The behavior of `SO_LINGER` is platform specific.

- #listen(backlog : Int = SOMAXCONN) : Nil

  Tells the previously bound socket to listen for incoming connections.

- #listen(backlog : Int = SOMAXCONN, &)

  Tries to listen for connections on the previously bound socket.

- #protocol : Protocol
- #receive(message : Bytes) : Tuple(Int32, Address)

  Receives a binary message from the previously bound address.

- #receive(max_message_size = 512) : Tuple(String, Address)

  Receives a text message from the previously bound address.

- #recv_buffer_size : Int32
- #recv_buffer_size=(val : Int32)
- #reuse_address=(val : Bool)
- #reuse_address? : Bool
- #reuse_port=(val : Bool)
- #reuse_port? : Bool
- #send(message, to addr : Address) : Int32

  Sends a message to the specified remote address.

- #send(message) : Int32

  Sends a message to a previously connected remote address.

- #send_buffer_size : Int32
- #send_buffer_size=(val : Int32)
- #tty?

  Returns `true` if this `IO` is associated with a terminal device (tty), `false` otherwise.

- #type : Type

### Class methods inherited from module `Crystal::System::Socket`

fcntl(fd, cmd, arg = 0) fcntl

### Instance methods inherited from module `IO::Evented`

evented_close : Nil evented_close, evented_read(slice : Bytes, errno_msg : String, &) : Int32 evented_read, evented_reopen : Nil evented_reopen, evented_send(slice : Bytes, errno_msg : String, &) : Int32 evented_send, evented_write(slice : Bytes, errno_msg : String, &) : Nil evented_write, read_timeout : Time::Span | Nil read_timeout, read_timeout=(read_timeout : Number) : Number
read_timeout=(timeout : Time::Span | Nil) : Time::Span | Nil read_timeout=, write_timeout : Time::Span | Nil write_timeout, write_timeout=(write_timeout : Number) : Number
write_timeout=(timeout : Time::Span | Nil) : Time::Span | Nil write_timeout=

### Instance methods inherited from module `IO::Buffered`

buffer_size : Int32 buffer_size, buffer_size=(value) buffer_size=, close : Nil close, flush flush, flush_on_newline=(flush_on_newline) flush_on_newline=, flush_on_newline? : Bool flush_on_newline?, peek : Bytes peek, pos : Int64 pos, read(slice : Bytes) : Int32 read, read_buffering=(read_buffering) read_buffering=, read_buffering? : Bool read_buffering?, rewind rewind, sync=(sync) sync=, sync? : Bool sync?, unbuffered_close unbuffered_close, unbuffered_flush unbuffered_flush, unbuffered_read(slice : Bytes) unbuffered_read, unbuffered_rewind unbuffered_rewind, unbuffered_write(slice : Bytes) unbuffered_write, write(slice : Bytes) : Nil write

### Instance methods inherited from class `IO`

<<(obj) : self <<, close close, closed? : Bool closed?, each_byte(&) : Nil
each_byte each_byte, each_char(&) : Nil
each_char each_char, each_line(*args, **options, &block : String -> ) : Nil
each_line(*args, **options) each_line, encoding : String encoding, flush flush, getb_to_end : Bytes getb_to_end, gets(limit : Int, chomp = false) : String | Nil
gets(delimiter : Char, limit : Int, chomp = false) : String | Nil
gets(delimiter : Char, chomp = false) : String | Nil
gets(delimiter : String, chomp = false) : String | Nil
gets(chomp = true) : String | Nil gets, gets_to_end : String gets_to_end, peek : Bytes | Nil peek, pos pos, pos=(value) pos=, print(obj : _) : Nil
print(*objects : _) : Nil print, printf(format_string, args : Array | Tuple) : Nil
printf(format_string, *args) : Nil printf, puts(string : String) : Nil
puts(obj : _) : Nil
puts : Nil
puts(*objects : _) : Nil puts, read(slice : Bytes) read, read_at(offset, bytesize, & : IO -> ) read_at, read_byte : UInt8 | Nil read_byte, read_bytes(type, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) read_bytes, read_char : Char | Nil read_char, read_fully(slice : Bytes) : Int32 read_fully, read_fully?(slice : Bytes) : Int32 | Nil read_fully?, read_line(*args, **options) : String read_line, read_string(bytesize : Int) : String read_string, read_utf8(slice : Bytes) read_utf8, read_utf8_byte : UInt8 | Nil read_utf8_byte, rewind rewind, seek(offset, whence : Seek = Seek::Set) seek, set_encoding(encoding : String, invalid : Symbol | Nil = nil) : Nil set_encoding, skip(bytes_count : Int) : Nil skip, skip_to_end : Nil skip_to_end, tell tell, tty? : Bool tty?, write(slice : Bytes) : Nil write, write_byte(byte : UInt8) : Nil write_byte, write_bytes(object, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) : Nil write_bytes, write_string(slice : Bytes) : Nil write_string, write_utf8(slice : Bytes) : Nil write_utf8

### Class methods inherited from class `IO`

copy(src, dst, limit : Int) : Int64
copy(src, dst) : Int64 copy, pipe(read_blocking = false, write_blocking = false) : Tuple(IO::FileDescriptor, IO::FileDescriptor)
pipe(read_blocking = false, write_blocking = false, &) pipe, same_content?(stream1 : IO, stream2 : IO) : Bool same_content?

### Instance methods inherited from class `Reference`

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

### Constructor methods inherited from class `Reference`

new new, unsafe_construct(address : Pointer, *args, **opts) : self unsafe_construct

### Class methods inherited from class `Reference`

pre_initialize(address : Pointer) pre_initialize

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.new(family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false) #
def self.new(fd, family : Family, type : Type, protocol : Protocol = Protocol::IP, blocking = false) #

Creates a Socket from an existing socket file descriptor / handle.

def self.tcp(family : Family, blocking = false) : self #

Creates a TCP socket. Consider using `TCPSocket` or `TCPServer` unless you need full control over the socket.

def self.unix(type : Type = Type::STREAM, blocking = false) : self #

Creates an UNIX socket. Consider using `UNIXSocket` or `UNIXServer` unless you need full control over the socket.

##
Class Method Detail

def self.fcntl(fd, cmd, arg = 0) #
def self.ip?(string : String) #

Returns `true` if the string represents a valid IPv4 or IPv6 address.

DEPRECATED Use `IPAddress.valid?` instead

def self.udp(family : Family, blocking = false) #

Creates an UDP socket. Consider using `UDPSocket` unless you need full control over the socket.

##
Instance Method Detail

def accept : Socket #

Accepts an incoming connection.

Returns the client socket. Raises an `IO::Error` (closed stream) exception if the server is closed after invoking this method.

    require "socket"

    server = TCPServer.new(2202)
    socket = server.accept
    socket.puts Time.utc
    socket.close

def accept? : Socket | Nil #

Accepts an incoming connection.

Returns the client `Socket` or `nil` if the server is closed after invoking this method.

    require "socket"

    server = TCPServer.new(2202)
    if socket = server.accept?
      socket.puts Time.utc
      socket.close
    end

def bind(host : String, port : Int) : Nil #

Binds the socket to a local address.

    require "socket"

    sock = Socket.tcp(Socket::Family::INET)
    sock.bind "localhost", 1234

def bind(port : Int) #

Binds the socket on port to all local interfaces.

    require "socket"

    sock = Socket.tcp(Socket::Family::INET6)
    sock.bind 1234

def bind(addr : Socket::Address) : Nil #

Binds the socket to a local address.

    require "socket"

    sock = Socket.udp(Socket::Family::INET)
    sock.bind Socket::IPAddress.new("192.168.1.25", 80)

def blocking #
def blocking=(value) #
def broadcast=(val : Bool) #
def broadcast? : Bool #
def close_on_exec=(arg : Bool) #
def close_on_exec? #
def close_read #

Calls `shutdown(2)` with `SHUT_RD`

def close_write #

Calls `shutdown(2)` with `SHUT_WR`

def closed? : Bool #
Description copied from class IO

Returns `true` if this `IO` is closed.

`IO` defines returns `false`, but including types may override.

def connect(host : String, port : Int, connect_timeout = nil) : Nil #

Connects the socket to a remote host:port.

    require "socket"

    sock = Socket.tcp(Socket::Family::INET)
    sock.connect "crystal-lang.org", 80

def connect(addr, timeout = nil) : Nil #

Connects the socket to a remote address. Raises if the connection failed.

    require "socket"

    sock = Socket.unix
    sock.connect Socket::UNIXAddress.new("/tmp/service.sock")

def connect(addr, timeout = nil, &) #

Tries to connect to a remote address. Yields an `IO::TimeoutError` or an `Socket::ConnectError` error if the connection failed.

def family : Family #
def fcntl(cmd, arg = 0) #
def fd #

Returns the handle associated with this socket from the operating system.

- on POSIX platforms, this is a file descriptor (`Int32`)
- on Windows, this is a SOCKET handle (`LibC::SOCKET`)

def finalize #
def inspect(io : IO) : Nil #
Description copied from class Reference

Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

    class Person
      def initialize(@name : String, @age : Int32)
      end
    end

    Person.new("John", 32).inspect # => #<Person:0x10fd31f20 @name="John", @age=32>

def keepalive=(val : Bool) #
def keepalive? #
def linger #
def linger=(val : Int | Nil) #

WARNING The behavior of `SO_LINGER` is platform specific. Bad things may happen especially with nonblocking sockets. See Cross-Platform Testing of SO_LINGER by Nybek for more information.

- `nil`: disable `SO_LINGER`
- `Int`: enable `SO_LINGER` and set timeout to `Int` seconds
  - `0`: abort on close (socket buffer is discarded and RST sent to peer). Depends on platform and whether `shutdown()` was called first.
  - `>=1`: abort after `Int` seconds on close. Linux and Cygwin may block on close.

def listen(backlog : Int = SOMAXCONN) : Nil #

Tells the previously bound socket to listen for incoming connections.

def listen(backlog : Int = SOMAXCONN, &) #

Tries to listen for connections on the previously bound socket. Yields an `Socket::Error` on failure.

def protocol : Protocol #
def receive(message : Bytes) : Tuple(Int32, Address) #

Receives a binary message from the previously bound address.

    require "socket"

    server = Socket.udp(Socket::Family::INET)
    server.bind("localhost", 1234)

    message = Bytes.new(32)
    bytes_read, client_addr = server.receive(message)

def receive(max_message_size = 512) : Tuple(String, Address) #

Receives a text message from the previously bound address.

    require "socket"

    server = Socket.udp(Socket::Family::INET)
    server.bind("localhost", 1234)

    message, client_addr = server.receive

def recv_buffer_size : Int32 #
def recv_buffer_size=(val : Int32) #
def reuse_address=(val : Bool) #
def reuse_address? : Bool #
def reuse_port=(val : Bool) #
def reuse_port? : Bool #
def send(message, to addr : Address) : Int32 #

Sends a message to the specified remote address.

    require "socket"

    server = Socket::IPAddress.new("10.0.3.1", 2022)
    sock = Socket.udp(Socket::Family::INET)
    sock.connect("example.com", 2000)
    sock.send("text query", to: server)

def send(message) : Int32 #

Sends a message to a previously connected remote address.

    require "socket"

    sock = Socket.udp(Socket::Family::INET)
    sock.connect("example.com", 2000)
    sock.send("text message")

    sock = Socket.unix(Socket::Type::DGRAM)
    sock.connect Socket::UNIXAddress.new("/tmp/service.sock")
    sock.send(Bytes[0])

def send_buffer_size : Int32 #
def send_buffer_size=(val : Int32) #
def tty? #
Description copied from class IO

Returns `true` if this `IO` is associated with a terminal device (tty), `false` otherwise.

IO returns `false`, but including types may override.

    STDIN.tty?          # => true
    IO::Memory.new.tty? # => false

def type : Type #