# 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
- #read_timeout : Time::Span | Nil

  The time to wait when reading before raising an `IO::TimeoutError`.

- #read_timeout=(read_timeout : Time::Span | Nil)

  The time to wait when reading before raising an `IO::TimeoutError`.

- #read_timeout=(read_timeout : Number) : Number

  Sets the number of seconds to wait when reading before raising an `IO::TimeoutError`.

  DEPRECATED Use `#read_timeout=(Time::Span?)` instead.

- #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
- #write_timeout : Time::Span | Nil

  Sets the time to wait when writing before raising an `IO::TimeoutError`.

- #write_timeout=(write_timeout : Time::Span | Nil)

  Sets the time to wait when writing before raising an `IO::TimeoutError`.

- #write_timeout=(write_timeout : Number) : Number

  Sets the number of seconds to wait when writing before raising an `IO::TimeoutError`.

  DEPRECATED Use `#write_timeout=(Time::Span?)` instead.

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

fcntl(fd, cmd, arg = 0) fcntl, socketpair(type : ::Socket::Type, protocol : ::Socket::Protocol) : Tuple(Handle, Handle) socketpair

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

evented_close : Nil evented_close, evented_read(errno_msg : String, &) : Int32 evented_read, evented_write(errno_msg : String, &) : Int32 evented_write

### 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 read_timeout : Time::Span | Nil #

The time to wait when reading before raising an `IO::TimeoutError`.

def read_timeout=(read_timeout : Time::Span | Nil) #

The time to wait when reading before raising an `IO::TimeoutError`.

def read_timeout=(read_timeout : Number) : Number #

Sets the number of seconds to wait when reading before raising an `IO::TimeoutError`.

DEPRECATED Use `#read_timeout=(Time::Span?)` instead.

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. Returns the number of bytes sent. Does not guarantee that the entire message is sent. That's only the case when the return value is equivalent to `message.bytesize`. `#write` ensures the entire message is sent but it requires an established connection.

    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. Returns the number of bytes sent. Does not guarantee that the entire message is sent. That's only the case when the return value is equivalent to `message.bytesize`. `#write` ensures the entire message is sent.

    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 #
def write_timeout : Time::Span | Nil #

Sets the time to wait when writing before raising an `IO::TimeoutError`.

def write_timeout=(write_timeout : Time::Span | Nil) #

Sets the time to wait when writing before raising an `IO::TimeoutError`.

def write_timeout=(write_timeout : Number) : Number #

Sets the number of seconds to wait when writing before raising an `IO::TimeoutError`.

DEPRECATED Use `#write_timeout=(Time::Span?)` instead.