Client-side network services for games and such

The following code implements a client to connect to a local server and briefly exchange with it.

redef fun handshake_app_name do return "nitwork_test"
redef fun handshake_app_version do return "1.0"

# Prepare connection with remote server
var config = new RemoteServerConfig("localhost", 4444)
var server = new RemoteServer(config)

# Try to connect
if not server.connect then return

# Make sure the server is compatible
if not server.handshake then return

# Connection up! communicate
server.writer.serialize "hello server"
print server.reader.deserialize.as(Object)

# Done, close socket
server.socket.close

Introduced classes

class RemoteServer

gamnit :: RemoteServer

Connection to a remote server
class RemoteServerConfig

gamnit :: RemoteServerConfig

Information of the remove server

Redefined classes

redef class Sys

gamnit :: client $ Sys

The main class of the program.

All class definitions

class RemoteServer

gamnit $ RemoteServer

Connection to a remote server
class RemoteServerConfig

gamnit $ RemoteServerConfig

Information of the remove server
redef class Sys

gamnit :: client $ Sys

The main class of the program.
package_diagram gamnit::client client gamnit::common common gamnit::client->gamnit::common socket socket gamnit::common->socket msgpack msgpack gamnit::common->msgpack ...socket ... ...socket->socket ...msgpack ... ...msgpack->msgpack gamnit::network network gamnit::network->gamnit::client a_star-m a_star-m a_star-m->gamnit::network a_star-m... ... a_star-m...->a_star-m

Ancestors

module abstract_collection

core :: abstract_collection

Abstract collection classes and services.
module abstract_text

core :: abstract_text

Abstract class for manipulation of sequences of characters
module array

core :: array

This module introduces the standard array structure.
module binary

binary :: binary

Read and write binary data with any Reader and Writer
module bitset

core :: bitset

Services to handle BitSet
module bytes

core :: bytes

Services for byte streams and arrays
module caching

serialization :: caching

Services for caching serialization engines
module circular_array

core :: circular_array

Efficient data structure to access both end of the sequence.
module codec_base

core :: codec_base

Base for codecs to use with streams
module codecs

core :: codecs

Group module for all codec-related manipulations
module collection

core :: collection

This module define several collection classes.
module core

core :: core

Standard classes and methods used by default by Nit programs and libraries.
module engine_tools

serialization :: engine_tools

Advanced services for serialization engines
module environ

core :: environ

Access to the environment variables of the process
module error

json :: error

Intro JsonParseError which is exposed by all JSON reading APIs
module error

core :: error

Standard error-management infrastructure.
module exec

core :: exec

Invocation and management of operating system sub-processes.
module ext

msgpack :: ext

Application specific MessagePack extension MsgPackExt
module file

core :: file

File manipulations (create, read, write, etc.)
module fixed_ints

core :: fixed_ints

Basic integers of fixed-precision
module fixed_ints_text

core :: fixed_ints_text

Text services to complement fixed_ints
module flat

core :: flat

All the array-based text representations
module gc

core :: gc

Access to the Nit internal garbage collection mechanism
module hash_collection

core :: hash_collection

Introduce HashMap and HashSet.
module inspect

serialization :: inspect

Refine Serializable::inspect to show more useful information
module iso8859_1

core :: iso8859_1

Codec for ISO8859-1 I/O
module json

json :: json

Read and write JSON formatted text using the standard serialization services
module kernel

core :: kernel

Most basic classes and methods.
module list

core :: list

This module handle double linked lists
module math

core :: math

Mathematical operations
module meta

meta :: meta

Simple user-defined meta-level to manipulate types of instances as object.
module msgpack

msgpack :: msgpack

MessagePack, an efficient binary serialization format
module native

core :: native

Native structures for text and bytes
module numeric

core :: numeric

Advanced services for Numeric types
module parser_base

parser_base :: parser_base

Simple base for hand-made parsers of all kinds
module poset

poset :: poset

Pre order sets and partial order set (ie hierarchies)
module protocol

core :: protocol

module queue

core :: queue

Queuing data structures and wrappers
module range

core :: range

Module for range of discrete objects.
module re

core :: re

Regular expression support for all services based on Pattern
module read

msgpack :: read

Low-level read MessagePack format from Reader streams
module ropes

core :: ropes

Tree-based representation of a String.
module safe

serialization :: safe

Services for safer deserialization engines
module serialization

serialization :: serialization

General serialization services
module serialization_common

msgpack :: serialization_common

Serialization services for serialization_write and serialization_read
module serialization_core

serialization :: serialization_core

Abstract services to serialize Nit objects to different formats
module serialization_read

msgpack :: serialization_read

Deserialize full Nit objects from MessagePack format
module serialization_read

json :: serialization_read

Services to read JSON: deserialize_json and JsonDeserializer
module serialization_write

msgpack :: serialization_write

Serialize full Nit objects to MessagePack format
module serialization_write

json :: serialization_write

Services to write Nit objects to JSON strings: serialize_to_json and JsonSerializer
module socket

socket :: socket

Socket services
module socket_c

socket :: socket_c

Low-level socket functionalities
module sorter

core :: sorter

This module contains classes used to compare things and sorts arrays.
module static

json :: static

Static interface to read Nit objects from JSON strings
module stream

core :: stream

Input and output streams of characters
module text

core :: text

All the classes and methods related to the manipulation of text entities
module time

core :: time

Management of time and dates
module union_find

core :: union_find

union–find algorithm using an efficient disjoint-set data structure
module utf8

core :: utf8

Codec for UTF-8 I/O
module write

msgpack :: write

Low-level write in MessagePack format to Writer streams

Parents

module common

gamnit :: common

Services common to the client and server modules

Children

module network

gamnit :: network

Easy client/server logic for games and simple distributed applications

Descendants

module a_star-m

a_star-m

# Client-side network services for games and such
#
# The following code implements a client to connect to a local server and
# briefly exchange with it.
#
# ~~~
# redef fun handshake_app_name do return "nitwork_test"
# redef fun handshake_app_version do return "1.0"
#
# # Prepare connection with remote server
# var config = new RemoteServerConfig("localhost", 4444)
# var server = new RemoteServer(config)
#
# # Try to connect
# if not server.connect then return
#
# # Make sure the server is compatible
# if not server.handshake then return
#
# # Connection up! communicate
# server.writer.serialize "hello server"
# print server.reader.deserialize.as(Object)
#
# # Done, close socket
# server.socket.close
# ~~~
module client

intrude import common

# Information of the remove server
class RemoteServerConfig

	# Address of the remote server, either a domain name or an Internet address
	var address: Text

	# Listening port of the server
	var port: Int
end

# Connection to a remote server
class RemoteServer

	# `RemoteServerConfig` used to initiate connection to the server
	var config: RemoteServerConfig

	# Communication socket with the server
	var socket: nullable TCPStream = null

	# Is this connection connected?
	fun connected: Bool
	do
		var socket = socket
		return socket != null and socket.connected
	end

	# `MsgPackSerializer` used to send data to this client through `socket`
	var writer: MsgPackSerializer is noinit

	# `MsgPackDeserializer` used to receive data from this client through `socket`
	var reader: MsgPackDeserializer is noinit

	# Attempt connection with the remote server
	fun connect: Bool
	do
		print "Connecting to {config.address}:{config.port}..."
		var socket = new TCPStream.connect(config.address.to_s, config.port)
		self.socket = socket

		if not socket.connected then
			print "Connection failed: {socket.last_error or else "Internal error"}"
			return false
		end

		# Setup serialization
		writer = new MsgPackSerializer(socket)
		writer.cache = new AsyncCache(false)
		reader = new MsgPackDeserializer(socket)
		writer.link reader

		return true
	end

	# Attempt handshake with server
	#
	# Validates compatibility between `handshake_app_name` and `handshake_app_version`.
	#
	# On error, close `socket`.
	fun handshake: Bool
	do
		# The client goes first so that the server doesn't show its hand
		var socket = socket
		assert socket != null

		# App name
		var app_name = sys.handshake_app_name
		socket.serialize_msgpack app_name

		var server_app = socket.deserialize_msgpack("String")
		if server_app != app_name then
			print_error "Handshake Error: server app name is '{server_app or else "<invalid>"}'"
			socket.close
			return false
		end

		# App version
		socket.serialize_msgpack sys.handshake_app_version

		var server_version = socket.deserialize_msgpack("String")
		if server_version != sys.handshake_app_version then
			print_error "Handshake Error: server version is different '{server_version or else "<invalid>"}'"
			socket.close
			return false
		end

		return true
	end
end

# Discover local servers responding on UDP `discovery_port`
#
# Sends a message in the format `gamnit::network? handshake_app_name` and
# looks for the response `gamnit::network! handshake_app_name port_number`.
# Waits for `timeout`, or the default 0.1 seconds, after sending the message.
#
# The server usually responds using the method `answer_discovery_requests`.
# When receiving responses, the client may then choose a server and
# connect via `new RemoteServer`.
#
# ~~~
# var servers = discover_local_servers
# if servers.not_empty then
#     var server = new RemoteServer(servers.first)
#     server.connect
#     server.writer.serialize "hello server"
#     server.socket.close
# end
# ~~~
fun discover_local_servers(timeout: nullable Float): Array[RemoteServerConfig]
do
	timeout = timeout or else 0.1

	var s = new UDPSocket
	s.enable_broadcast = true
	s.blocking = false
	s.broadcast(discovery_port, "{discovery_request_message} {handshake_app_name}")
	timeout.sleep

	var r = new Array[RemoteServerConfig]
	loop
		var ptr = new Ref[nullable SocketAddress](null)
		var resp = s.recv_from(1024, ptr)
		var src = ptr.item

		if resp.is_empty then
			# No response
			break
		else
			assert src != null
			var words = resp.split(" ")
			if words.length == 3 and words[0] == discovery_response_message and
			   words[1] == handshake_app_name and words[2].is_int then
				var address = src.address
				var port = words[2].to_i
				r.add new RemoteServerConfig(address, port)
			end
		end
	end
	return r
end
lib/gamnit/network/client.nit:15,1--184,3