367 lines
13 KiB
Plaintext
367 lines
13 KiB
Plaintext
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/**
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@page Tutorial Tutorial
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@ref Initialization
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@ref CreateServer
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@ref CreateClient
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@ref ManageHost
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@ref SendingPacket
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@ref Disconnecting
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@ref Connecting
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@section Initialization Initialization
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You should include the file <enet/enet.h> when using ENet. Do not
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include <enet.h> without the directory prefix, as this may cause
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file name conflicts on some systems.
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Before using ENet, you must call enet_initialize() to initialize the
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library. Upon program exit, you should call enet_deinitialize() so
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that the library may clean up any used resources.
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@code
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#include <enet/enet.h>
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int
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main (int argc, char ** argv)
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{
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if (enet_initialize () != 0)
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{
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fprintf (stderr, "An error occurred while initializing ENet.\n");
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return EXIT_FAILURE;
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}
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atexit (enet_deinitialize);
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...
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...
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...
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}
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@endcode
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@section CreateServer Creating an ENet server
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Servers in ENet are constructed with enet_host_create(). You must
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specify an address on which to receive data and new connections, as
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well as the maximum allowable numbers of connected peers. You may
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optionally specify the incoming and outgoing bandwidth of the server
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in bytes per second so that ENet may try to statically manage
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bandwidth resources among connected peers in addition to its dynamic
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throttling algorithm; specifying 0 for these two options will cause
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ENet to rely entirely upon its dynamic throttling algorithm to manage
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bandwidth.
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When done with a host, the host may be destroyed with
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enet_host_destroy(). All connected peers to the host will be reset,
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and the resources used by the host will be freed.
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@code
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ENetAddress address;
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ENetHost * server;
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/* Bind the server to the default localhost. */
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/* A specific host address can be specified by */
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/* enet_address_set_host (& address, "x.x.x.x"); */
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address.host = ENET_HOST_ANY;
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/* Bind the server to port 1234. */
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address.port = 1234;
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server = enet_host_create (& address /* the address to bind the server host to */,
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32 /* allow up to 32 clients and/or outgoing connections */,
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2 /* allow up to 2 channels to be used, 0 and 1 */,
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0 /* assume any amount of incoming bandwidth */,
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0 /* assume any amount of outgoing bandwidth */);
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if (server == NULL)
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{
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fprintf (stderr,
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"An error occurred while trying to create an ENet server host.\n");
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exit (EXIT_FAILURE);
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}
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...
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...
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...
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enet_host_destroy(server);
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@endcode
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@section CreateClient Creating an ENet client
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Clients in ENet are similarly constructed with enet_host_create() when
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no address is specified to bind the host to. Bandwidth may be
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specified for the client host as in the above example. The peer count
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controls the maximum number of connections to other server hosts that
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may be simultaneously open.
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@code
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ENetHost * client;
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client = enet_host_create (NULL /* create a client host */,
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1 /* only allow 1 outgoing connection */,
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2 /* allow up 2 channels to be used, 0 and 1 */,
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57600 / 8 /* 56K modem with 56 Kbps downstream bandwidth */,
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14400 / 8 /* 56K modem with 14 Kbps upstream bandwidth */);
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if (client == NULL)
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{
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fprintf (stderr,
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"An error occurred while trying to create an ENet client host.\n");
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exit (EXIT_FAILURE);
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}
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...
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...
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...
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enet_host_destroy(client);
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@endcode
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@section ManageHost Managing an ENet host
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ENet uses a polled event model to notify the programmer of significant
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events. ENet hosts are polled for events with enet_host_service(),
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where an optional timeout value in milliseconds may be specified to
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control how long ENet will poll; if a timeout of 0 is specified,
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enet_host_service() will return immediately if there are no events to
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dispatch. enet_host_service() will return 1 if an event was dispatched
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within the specified timeout.
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Beware that most processing of the network with the ENet stack is done
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inside enet_host_service(). Both hosts that make up the sides of a connection
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must regularly call this function to ensure packets are actually sent and
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received. A common symptom of not actively calling enet_host_service()
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on both ends is that one side receives events while the other does not.
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The best way to schedule this activity to ensure adequate service is, for
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example, to call enet_host_service() with a 0 timeout (meaning non-blocking)
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at the beginning of every frame in a game loop.
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Currently there are only four types of significant events in ENet:
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An event of type ENET_EVENT_TYPE_NONE is returned if no event occurred
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within the specified time limit. enet_host_service() will return 0
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with this event.
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An event of type ENET_EVENT_TYPE_CONNECT is returned when either a new client
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host has connected to the server host or when an attempt to establish a
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connection with a foreign host has succeeded. Only the "peer" field of the
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event structure is valid for this event and contains the newly connected peer.
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An event of type ENET_EVENT_TYPE_RECEIVE is returned when a packet is received
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from a connected peer. The "peer" field contains the peer the packet was
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received from, "channelID" is the channel on which the packet was sent, and
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"packet" is the packet that was sent. The packet contained in the "packet"
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field must be destroyed with enet_packet_destroy() when you are done
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inspecting its contents.
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An event of type ENET_EVENT_TYPE_DISCONNECT is returned when a connected peer
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has either explicitly disconnected or timed out. Only the "peer" field of the
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event structure is valid for this event and contains the peer that
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disconnected. Only the "data" field of the peer is still valid on a
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disconnect event and must be explicitly reset.
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@code
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ENetEvent event;
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/* Wait up to 1000 milliseconds for an event. */
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while (enet_host_service (client, & event, 1000) > 0)
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{
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switch (event.type)
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{
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case ENET_EVENT_TYPE_CONNECT:
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printf ("A new client connected from %x:%u.\n",
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event.peer -> address.host,
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event.peer -> address.port);
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/* Store any relevant client information here. */
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event.peer -> data = "Client information";
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break;
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case ENET_EVENT_TYPE_RECEIVE:
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printf ("A packet of length %u containing %s was received from %s on channel %u.\n",
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event.packet -> dataLength,
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event.packet -> data,
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event.peer -> data,
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event.channelID);
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/* Clean up the packet now that we're done using it. */
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enet_packet_destroy (event.packet);
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break;
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case ENET_EVENT_TYPE_DISCONNECT:
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printf ("%s disconnected.\n", event.peer -> data);
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/* Reset the peer's client information. */
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event.peer -> data = NULL;
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}
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}
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...
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...
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...
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@endcode
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@section SendingPacket Sending a packet to an ENet peer
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Packets in ENet are created with enet_packet_create(), where the size
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of the packet must be specified. Optionally, initial data may be
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specified to copy into the packet.
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Certain flags may also be supplied to enet_packet_create() to control
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various packet features:
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ENET_PACKET_FLAG_RELIABLE specifies that the packet must use reliable
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delivery. A reliable packet is guaranteed to be delivered, and a
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number of retry attempts will be made until an acknowledgement is
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received from the foreign host the packet is sent to. If a certain
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number of retry attempts is reached without any acknowledgement, ENet
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will assume the peer has disconnected and forcefully reset the
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connection. If this flag is not specified, the packet is assumed an
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unreliable packet, and no retry attempts will be made nor
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acknowledgements generated.
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A packet may be resized (extended or truncated) with
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enet_packet_resize().
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A packet is sent to a foreign host with
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enet_peer_send(). enet_peer_send() accepts a channel id over which to
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send the packet to a given peer. Once the packet is handed over to
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ENet with enet_peer_send(), ENet will handle its deallocation and
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enet_packet_destroy() should not be used upon it.
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One may also use enet_host_broadcast() to send a packet to all
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connected peers on a given host over a specified channel id, as with
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enet_peer_send().
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Queued packets will be sent on a call to enet_host_service().
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Alternatively, enet_host_flush() will send out queued packets without
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dispatching any events.
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@code
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/* Create a reliable packet of size 7 containing "packet\0" */
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ENetPacket * packet = enet_packet_create ("packet",
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strlen ("packet") + 1,
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ENET_PACKET_FLAG_RELIABLE);
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/* Extend the packet so and append the string "foo", so it now */
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/* contains "packetfoo\0" */
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enet_packet_resize (packet, strlen ("packetfoo") + 1);
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strcpy (& packet -> data [strlen ("packet")], "foo");
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/* Send the packet to the peer over channel id 0. */
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/* One could also broadcast the packet by */
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/* enet_host_broadcast (host, 0, packet); */
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enet_peer_send (peer, 0, packet);
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...
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...
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...
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/* One could just use enet_host_service() instead. */
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enet_host_flush (host);
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@endcode
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@section Disconnecting Disconnecting an ENet peer
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Peers may be gently disconnected with enet_peer_disconnect(). A
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disconnect request will be sent to the foreign host, and ENet will
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wait for an acknowledgement from the foreign host before finally
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disconnecting. An event of type ENET_EVENT_TYPE_DISCONNECT will be
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generated once the disconnection succeeds. Normally timeouts apply to
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the disconnect acknowledgement, and so if no acknowledgement is
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received after a length of time the peer will be forcefully
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disconnected.
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enet_peer_reset() will forcefully disconnect a peer. The foreign host
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will get no notification of a disconnect and will time out on the
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foreign host. No event is generated.
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@code
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ENetEvent event;
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enet_peer_disconnect (peer, 0);
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/* Allow up to 3 seconds for the disconnect to succeed
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* and drop any packets received packets.
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*/
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while (enet_host_service (client, & event, 3000) > 0)
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{
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switch (event.type)
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{
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case ENET_EVENT_TYPE_RECEIVE:
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enet_packet_destroy (event.packet);
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break;
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case ENET_EVENT_TYPE_DISCONNECT:
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puts ("Disconnection succeeded.");
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return;
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...
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...
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...
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}
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}
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/* We've arrived here, so the disconnect attempt didn't */
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/* succeed yet. Force the connection down. */
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enet_peer_reset (peer);
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...
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...
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...
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@endcode
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@section Connecting Connecting to an ENet host
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A connection to a foreign host is initiated with enet_host_connect().
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It accepts the address of a foreign host to connect to, and the number
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of channels that should be allocated for communication. If N channels
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are allocated for use, their channel ids will be numbered 0 through
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N-1. A peer representing the connection attempt is returned, or NULL
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if there were no available peers over which to initiate the
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connection. When the connection attempt succeeds, an event of type
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ENET_EVENT_TYPE_CONNECT will be generated. If the connection attempt
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times out or otherwise fails, an event of type
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ENET_EVENT_TYPE_DISCONNECT will be generated.
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@code
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ENetAddress address;
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ENetEvent event;
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ENetPeer *peer;
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/* Connect to some.server.net:1234. */
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enet_address_set_host (& address, "some.server.net");
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address.port = 1234;
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/* Initiate the connection, allocating the two channels 0 and 1. */
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peer = enet_host_connect (client, & address, 2, 0);
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if (peer == NULL)
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{
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fprintf (stderr,
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"No available peers for initiating an ENet connection.\n");
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exit (EXIT_FAILURE);
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}
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/* Wait up to 5 seconds for the connection attempt to succeed. */
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if (enet_host_service (client, & event, 5000) > 0 &&
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event.type == ENET_EVENT_TYPE_CONNECT)
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{
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puts ("Connection to some.server.net:1234 succeeded.");
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...
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...
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...
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}
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else
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{
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/* Either the 5 seconds are up or a disconnect event was */
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/* received. Reset the peer in the event the 5 seconds */
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/* had run out without any significant event. */
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enet_peer_reset (peer);
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puts ("Connection to some.server.net:1234 failed.");
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}
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...
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...
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...
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@endcode
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*/
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