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authoreihrul <eihrul>2010-05-20 20:43:42 +0000
committereihrul <eihrul>2010-05-20 20:43:42 +0000
commitf34daadcf1d0c46be29ffaf3f60c5babec98230c (patch)
treed028c5bb783dcc56159d04189307233271ed6712
parent13c9411acf9f66a2d54d8c6b39d64f1ef2c25826 (diff)
downloadenet-f34daadcf1d0c46be29ffaf3f60c5babec98230c.tar.gz
enet-f34daadcf1d0c46be29ffaf3f60c5babec98230c.zip
removing stale files
-rw-r--r--design.txt117
-rw-r--r--tutorial.txt325
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diff --git a/design.txt b/design.txt
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-* Why ENet?
-
- ENet evolved specifically as a UDP networking layer for the multiplayer
-first person shooter Cube. Cube necessitated low latency communcation with
-data sent out very frequently, so TCP was an unsuitable choice due to its
-high latency and stream orientation. UDP, however, lacks many sometimes
-necessary features from TCP such as reliability, sequencing, unrestricted
-packet sizes, and connection management. So UDP by itself was not suitable
-as a network protocol either. No suitable freely available networking
-libraries existed at the time of ENet's creation to fill this niche.
-
- UDP and TCP could have been used together in Cube to benefit somewhat
-from both of their features, however, the resulting combinations of protocols
-still leaves much to be desired. TCP lacks multiple streams of communication
-without resorting to opening many sockets and complicates delineation of
-packets due to its buffering behavior. UDP lacks sequencing, connection
-management, management of bandwidth resources, and imposes limitations on
-the size of packets. A significant investment is required to integrate these
-two protocols, and the end result is worse off in features and performance
-than the uniform protocol presented by ENet.
-
- ENet thus attempts to address these issues and provide a single, uniform
-protocol layered over UDP to the developer with the best features of UDP and
-TCP as well as some useful features neither provide, with a much cleaner
-integration than any resulting from a mixture of UDP and TCP.
-
-* Connection management
-
- ENet provides a simple connection interface over which to communicate
-with a foreign host. The liveness of the connection is actively monitored
-by pinging the foreign host at frequent intervals, and also monitors the
-network conditions from the local host to the foreign host such as the
-mean round trip time and packet loss in this fashion.
-
-* Sequencing
-
- Rather than a single byte stream that complicates the delineation
-of packets, ENet presents connections as multiple, properly sequenced packet
-streams that simplify the transfer of various types of data.
-
- ENet provides sequencing for all packets by assigning to each sent
-packet a sequence number that is incremented as packets are sent. ENet
-guarentees that no packet with a higher sequence number will be delivered
-before a packet with a lower sequence number, thus ensuring packets are
-delivered exactly in the order they are sent.
-
- For unreliable packets, ENet will simply discard the lower sequence
-number packet if a packet with a higher sequence number has already been
-delivered. This allows the packets to be dispatched immediately as they
-arrive, and reduce latency of unreliable packets to an absolute minimum.
-For reliable packets, if a higher sequence number packet arrives, but the
-preceding packets in the sequence have not yet arrived, ENet will stall
-delivery of the higher sequence number packets until its predecessors
-have arrived.
-
-* Channels
-
- Since ENet will stall delivery of reliable packets to ensure proper
-sequencing, and consequently any packets of higher sequence number whether
-reliable or unreliable, in the event the reliable packet's predecessors
-have not yet arrived, this can introduce latency into the delivery of other
-packets which may not need to be as strictly ordered with respect to the
-packet that stalled their delivery.
-
- To combat this latency and reduce the ordering restrictions on packets,
-ENet provides multiple channels of communication over a given connection.
-Each channel is independently sequenced, and so the delivery status of
-a packet in one channel will not stall the delivery of other packets
-in another channel.
-
-* Reliability
-
- ENet provides optional reliability of packet delivery by ensuring the
-foreign host acknowledges receipt of all reliable packets. ENet will attempt
-to resend the packet up to a reasonable amount of times, if no acknowledgement
-of the packet's receipt happens within a specified timeout. Retry timeouts
-are progressive and become more lenient with every failed attempt to allow
-for temporary turbulence in network conditions.
-
-* Fragmentation and reassembly
-
- ENet will send and deliver packets regardless of size. Large packets are
-fragmented into many smaller packets of suitable size, and reassembled on
-the foreign host to recover the original packet for delivery. The process
-is entirely transparent to the developer.
-
-* Aggregation
-
- ENet aggregates all protocol commands, including acknowledgements and
-packet transfer, into larger protocol packets to ensure the proper utilization
-of the connection and to limit the opportunities for packet loss that might
-otherwise result in further delivery latency.
-
-* Adaptability
-
- ENet provides an in-flight data window for reliable packets to ensure
-connections are not overwhelmed by volumes of packets. It also provides a
-static bandwidth allocation mechanism to ensure the total volume of packets
-sent and received to a host don't exceed the host's capabilities. Further,
-ENet also provides a dynamic throttle that responds to deviations from normal
-network connections to rectify various types of network congestion by further
-limiting the volume of packets sent.
-
-* Portability
-
- ENet works on Windows and any other Unix or Unix-like platform providing
-a BSD sockets interface. The library has a small and stable code base that
-can easily be extended to support other platforms and integrates easily.
-
-* Freedom
-
- ENet demands no royalties and doesn't carry a viral license that would
-restrict you in how you might use it in your programs. ENet is licensed under
-a short-and-sweet MIT-style license, which gives you the freedom to do anything
-you want with it (well, almost anything).
-
-
diff --git a/tutorial.txt b/tutorial.txt
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-* Using ENet
-
- Before using ENet, you must call enet_initialize() to initialize the
-library. Upon program exit, you should call enet_deinitialize() so that
-the library may clean up any used resources.
-
-i.e.
-
-int
-main (int argc, char ** argv)
-{
- if (enet_initialize () != 0)
- {
- fprintf (stderror, "An error occurred while initializing ENet.\n");
- return EXIT_FAILURE;
- }
- atexit (enet_deinitialize);
- ...
- ...
- ...
-}
-
-* Creating an ENet server
-
- Servers in ENet are constructed with enet_host_create(). You must specify
-an address on which to receive data and new connections, as well as the maximum
-allowable numbers of connected peers. You may optionally specify the incoming
-and outgoing bandwidth of the server in bytes per second so that ENet may try
-to statically manage bandwidth resources among connected peers in addition to
-its dynamic throttling algorithm; specifying 0 for these two options will cause
-ENet to rely entirely upon its dynamic throttling algorithm to manage
-bandwidth.
-
- When done with a host, the host may be destroyed with enet_host_destroy().
-All connected peers to the host will be reset, and the resources used by
-the host will be freed.
-
-i.e.
-
- ENetAddress address;
- ENetHost * server;
-
- /* Bind the server to the default localhost.
- * A specific host address can be specified by
- * enet_address_set_host (& address, "x.x.x.x");
- */
- address.host = ENET_HOST_ANY;
- /* Bind the server to port 1234. */
- address.port = 1234;
-
- server = enet_host_create (& address /* the address to bind the server host to */,
- 32 /* allow up to 32 clients and/or outgoing connections */,
- 0 /* assume any amount of incoming bandwidth */,
- 0 /* assume any amount of outgoing bandwidth */);
- if (server == NULL)
- {
- fprintf (stderr,
- "An error occurred while trying to create an ENet server host.\n");
- exit (EXIT_FAILURE);
- }
- ...
- ...
- ...
- enet_host_destroy(server);
-
-* Creating an ENet client
-
- Clients in ENet are similarly constructed with enet_host_create() when no
-address is specified to bind the host to. Bandwidth may be specified for the
-client host as in the above example. The peer count controls the maximum number
-of connections to other server hosts that may be simultaneously open.
-
-i.e.
-
- ENetHost * client;
-
- clienet = enet_host_create (NULL /* create a client host */,
- 1 /* only allow 1 outgoing connection */,
- 57600 / 8 /* 56K modem with 56 Kbps downstream bandwidth */,
- 14400 / 8 /* 56K modem with 14 Kbps upstream bandwidth */);
-
- if (client == NULL)
- {
- fprintf (stderr,
- "An error occurred while trying to create an ENet client host.\n");
- exit (EXIT_FAILURE);
- }
- ...
- ...
- ...
- enet_host_destroy(client);
-
-* Managing an ENet host
-
- ENet uses a polled event model to notify the programmer of significant
-events. ENet hosts are polled for events with enet_host_service(), where an
-optional timeout value in milliseconds may be specified to control how long
-ENet will poll; if a timeout of 0 is specified, enet_host_service() will
-return immediately if there are no events to dispatch. enet_host_service()
-will return 1 if an event was dispatched within the specified timeout.
-
- Currently there are only four types of significant events in ENet:
-
-An event of type ENET_EVENT_TYPE_NONE is returned if no event occurred
-within the specified time limit. enet_host_service() will return 0
-with this event.
-
-An event of type ENET_EVENT_TYPE_CONNECT is returned when either a new client
-host has connected to the server host or when an attempt to establish a
-connection with a foreign host has succeeded. Only the "peer" field of the
-event structure is valid for this event and contains the newly connected peer.
-
-An event of type ENET_EVENT_TYPE_RECEIVE is returned when a packet is received
-from a connected peer. The "peer" field contains the peer the packet was
-received from, "channelID" is the channel on which the packet was sent, and
-"packet" is the packet that was sent. The packet contained in the "packet"
-field must be destroyed with enet_packet_destroy() when you are done
-inspecting its contents.
-
-An event of type ENET_EVENT_TYPE_DISCONNECT is returned when a connected peer
-has either explicitly disconnected or timed out. Only the "peer" field of the
-event structure is valid for this event and contains the peer that
-disconnected. Only the "data" field of the peer is still valid on a
-disconnect event and must be explicitly reset.
-
-i.e.
-
- ENetEvent event;
-
- /* Wait up to 1000 milliseconds for an event. */
- while (enet_host_service (client, & event, 1000) > 0)
- {
- switch (event.type)
- {
- case ENET_EVENT_TYPE_CONNECT:
- printf ("A new client connected from %x:%u.\n",
- event.peer -> address.host,
- event.peer -> address.port);
-
- /* Store any relevant client information here. */
- event.peer -> data = "Client information";
-
- break;
-
- case ENET_EVENT_TYPE_RECEIVE:
- printf ("A packet of length %u containing %s was received from %s on channel %u.\n",
- event.packet -> dataLength,
- event.packet -> data,
- event.peer -> data,
- event.channelID);
-
- /* Clean up the packet now that we're done using it. */
- enet_packet_destroy (event.packet);
-
- break;
-
- case ENET_EVENT_TYPE_DISCONNECT:
- printf ("%s disconected.\n", event.peer -> data);
-
- /* Reset the peer's client information. */
-
- event.peer -> data = NULL;
- }
- }
- ...
- ...
- ...
-
-* Sending a packet to an ENet peer
-
- Packets in ENet are created with enet_packet_create(), where the size of
-the packet must be specified. Optionally, initial data may be specified to
-copy into the packet.
-
- Certain flags may also be supplied to enet_packet_create() to control
-various packet features:
-
-ENET_PACKET_FLAG_RELIABLE specifies that the packet must use reliable delivery.
-A reliable packet is guarenteed to be delivered, and a number of retry attempts
-will be made until an acknowledgement is received from the foreign host the
-packet is sent to. If a certain number of retry attempts is reached without
-any acknowledgement, ENet will assume the peer has disconnected and forcefully
-reset the connection. If this flag is not specified, the packet is assumed
-an unreliable packet, and no retry attempts will be made nor acknowledgements
-generated.
-
- A packet may be resized (extended or truncated) with enet_packet_resize().
-
- A packet is sent to a foreign host with enet_peer_send(). enet_peer_send()
-accepts a channel id over which to send the packet to a given peer. Once the
-packet is handed over to ENet with enet_peer_send(), ENet will handle its
-deallocation and enet_packet_destroy() should not be used upon it.
-
- One may also use enet_host_broadcast() to send a packet to all connected
-peers on a given host over a specified channel id, as with enet_peer_send().
-
- Queued packets will be sent on a call to enet_host_service().
-Alternatively, enet_host_flush() will send out queued packets without
-dispatching any events.
-
-i.e.
-
- /* Create a reliable packet of size 7 containing "packet\0" */
- ENetPacket * packet = enet_packet_create ("packet",
- strlen ("packet") + 1,
- ENET_PACKET_FLAG_RELIABLE);
-
- /* Extend the packet so and append the string "foo", so it now
- * contains "packetfoo\0"
- *
- enet_packet_resize (packet, strlen ("packetfoo") + 1);
- strcpy (& packet -> data [strlen ("packet")], "foo");
-
- /* Send the packet to the peer over channel id 3.
- * One could also broadcast the packet by
- * enet_host_broadcast (host, 3, packet);
- */
- enet_peer_send (peer, 3, packet);
- ...
- ...
- ...
- /* One could just use enet_host_service() instead. */
- enet_host_flush (host);
-
-* Disconnecting an ENet peer
-
- Peers may be gently disconnected with enet_peer_disconnect(). A disconnect
-request will be sent to the foreign host, and ENet will wait for an
-acknowledgement from the foreign host before finally disconnecting. An
-event of type ENET_EVENT_TYPE_DISCONNECT will be generated once the
-disconnection succeeds. Normally timeouts apply to the disconnect
-acknowledgement, and so if no acknowledgement is received after a length
-of time the peer will be forcefully disconnected.
-
- enet_peer_reset() will forcefully disconnect a peer. The foreign host
-will get no notification of a disconnect and will time out on the foreign
-host. No event is generated.
-
-i.e.
- ENetEvent event;
-
- enet_peer_disconnect (& client -> peers [0], 0);
-
- /* Allow up to 3 seconds for the disconnect to succeed
- * and drop any packets received packets.
- */
- while (enet_host_service (client, & event, 3000) > 0)
- {
- switch (event.type)
- {
- case ENET_EVENT_TYPE_RECEIVE:
- enet_packet_destroy (event.packet);
- break;
-
- case ENET_EVENT_TYPE_DISCONNECT:
- puts ("Disconnection succeeded.");
- return;
- ...
- ...
- ...
- }
- }
-
- /* We've arrived here, so the disconnect attempt didn't succeed yet.
- * Force the connection down.
- */
- enet_peer_reset (& client -> peers [0]);
- ...
- ...
- ...
-
-* Connecting to an ENet host
-
- A connection to a foregin host is initiated with enet_host_connect().
-It accepts the address of a foreign host to connect to, and the number of
-channels that should be allocated for communication. If N channels are
-allocated for use, their channel ids will be numbered 0 through N-1.
-A peer representing the connection attempt is returned, or NULL if there
-were no available peers over which to initiate the connection. When the
-connection attempt succeeds, an event of type ENET_EVENT_TYPE_CONNECT will
-be generated. If the connection attempt times out or otherwise fails, an
-event of type ENET_EVENT_TYPE_DISCONNECT will be generated.
-
-i.e.
- ENetAddress address;
- ENetEvent event;
- ENetPeer *peer;
-
- /* Connect to some.server.net:1234. */
- enet_address_set_host (& address, "some.server.net");
- address.port = 1234;
-
- /* Initiate the connection, allocating the two channels 0 and 1. */
- peer = enet_host_connect (client, & address, 2);
-
- if (peer == NULL)
- {
- fprintf (stderr,
- "No available peers for initiating an ENet connection.\n");
- exit (EXIT_FAILURE);
- }
-
- /* Wait up to 5 seconds for the connection attempt to succeed.
- if (enet_host_service (client, & event, 5000) > 0 &&
- event.type == ENET_EVENT_TYPE_CONNECT)
- {
- puts ("Connection to some.server.net:1234 succeeded.");
- ...
- ...
- ...
- }
- else
- {
- /* Either the 5 seconds are up or a disconnect event was
- * received. Reset the peer in the event the 5 seconds
- * had run out without any significant event.
- */
- enet_peer_reset (peer);
-
- puts ("Connection to some.server.net:1234 failed.");
- }
- ...
- ...
- ...
-