require "socket"

server = TCPServer.new("localhost", 1234)
loop do
  server.accept do |client|
    message = client.gets
    client << message # echo the message back
  end
end

Instance methods inherited from module Socket::Server

accept(&block) accept, accept?(&block) accept?

Instance methods inherited from class TCPSocket

tcp_keepalive_count tcp_keepalive_count, tcp_keepalive_count=(val : Int) tcp_keepalive_count=, tcp_keepalive_idle tcp_keepalive_idle, tcp_keepalive_idle=(val : Int) tcp_keepalive_idle=, tcp_keepalive_interval tcp_keepalive_interval, tcp_keepalive_interval=(val : Int) tcp_keepalive_interval=, tcp_nodelay=(val : Bool) tcp_nodelay=, tcp_nodelay? tcp_nodelay?

Constructor methods inherited from class TCPSocket

new(fd : Int32, family : Family, type : Type, protocol : Protocol)
new(family : Family, type : Type, protocol : Protocol)
new(host, port, dns_timeout = nil, connect_timeout = nil)
new(family : Family = Family::INET) new

Class methods inherited from class TCPSocket

open(host, port, &block) open

Instance methods inherited from class IPSocket

local_address local_address, remote_address remote_address

Instance methods inherited from class Socket

accept accept, accept? accept?, bind(host : String, port : Int)
bind(port : Int)
bind(addr)
bind(addr, &block) bind, broadcast=(val : Bool) broadcast=, broadcast? broadcast?, close_read close_read, close_write close_write, connect(host : String, port : Int, connect_timeout = nil)
connect(addr, timeout = nil) : Nil
connect(addr, timeout = nil, &block) connect, family : Family family, getsockopt(optname, optval, level = LibC::SOL_SOCKET) getsockopt, inspect(io) inspect, keepalive=(val : Bool) keepalive=, keepalive? keepalive?, linger linger, linger=(val : Int?) linger=, listen(backlog = SOMAXCONN)
listen(backlog = SOMAXCONN, &block) listen, protocol : Protocol protocol, receive(max_message_size = 512) : Tuple(String, Address)
receive(message : Bytes) : Tuple(Int32, Address) receive, recv_buffer_size recv_buffer_size, recv_buffer_size=(val : Int32) recv_buffer_size=, reuse_address=(val : Bool) reuse_address=, reuse_address? reuse_address?, reuse_port=(val : Bool) reuse_port=, reuse_port? reuse_port?, send(message, to addr : Address)
send(message) send, send_buffer_size send_buffer_size, send_buffer_size=(val : Int32) send_buffer_size=, setsockopt(optname, optval, level = LibC::SOL_SOCKET) setsockopt, type : Type type

Constructor methods inherited from class Socket

new(fd : Int32, family, type, protocol = Protocol::IP)
new(family, type, protocol = Protocol::IP, blocking = false) new

Class methods inherited from class Socket

ip?(string : String) ip?, tcp(family : Family, blocking = false) tcp, udp(family : Family, blocking = false) udp, unix(type : Type = Type::STREAM, blocking = false) unix

Instance methods inherited from class IO::FileDescriptor

blocking blocking, blocking=(value) blocking=, close_on_exec=(arg : Bool) close_on_exec=, close_on_exec? close_on_exec?, closed? : Bool closed?, cooked(&block) cooked, cooked! cooked!, fcntl(cmd, arg = 0) fcntl, fd : Int32 fd, finalize finalize, inspect(io) inspect, noecho(&block) noecho, noecho! noecho!, pos pos, pos=(value) pos=, pretty_print(pp) pretty_print, raw(&block) raw, raw! raw!, read_timeout=(read_timeout : Time::Span)
read_timeout=(read_timeout : Nil)
read_timeout=(read_timeout : Number) read_timeout=, reopen(other : IO::FileDescriptor) reopen, seek(offset, whence : Seek = Seek::Set)
seek(offset, whence : Seek = Seek::Set, &block) seek, stat stat, tell tell, tty? tty?, write_timed_out : Bool write_timed_out, write_timed_out=(write_timed_out : Bool) write_timed_out=, write_timeout=(write_timeout : Number)
write_timeout=(write_timeout : Time::Span)
write_timeout=(write_timeout : Nil) write_timeout=

Constructor methods inherited from class IO::FileDescriptor

new(fd : Int32, blocking = false, edge_triggerable = false) new

Class methods inherited from class IO::FileDescriptor

fcntl(fd, cmd, arg = 0) fcntl

Instance methods inherited from module IO::Buffered

close : Nil close, flush flush, flush_on_newline=(flush_on_newline) flush_on_newline=, flush_on_newline? flush_on_newline?, peek : Bytes? peek, read(slice : Bytes) read, rewind rewind, sync=(sync) sync=, sync? 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) write

Instance methods inherited from module IO

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

Class methods inherited from module IO

copy(src, dst, limit : Int)
copy(src, dst) copy, pipe(read_blocking = false, write_blocking = false)
pipe(read_blocking = false, write_blocking = false, &block) pipe

Instance methods inherited from class Reference

==(other : self)
==(other) ==, dup dup, hash hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference)
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

Constructor methods inherited from class Reference

new new

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, class class, dup dup, hash hash, inspect(io : IO)
inspect inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&block) tap, to_json(io : IO)
to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s
to_s(io : IO) to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&block) try, unsafe_as(type : T.class) forall T unsafe_as

Constructor methods inherited from class Object

from_json(string_or_io, root : String) : self
from_json(string_or_io) : self from_json, from_yaml(string_or_io) : self from_yaml

require "socket"

server = TCPServer.new(2022)
loop do
  if socket = server.accept?
    # handle the client in a fiber
    spawn handle_connection(socket)
  else
    # another fiber closed the server
    break
  end
end