NetworkedMultiplayerENet

Inherits: NetworkedMultiplayerPeer < PacketPeer < Reference < Object

PacketPeer implementation using the ENet library.

Description

A PacketPeer implementation that should be passed to SceneTree.network_peer after being initialized as either a client or server. Events can then be handled by connecting to SceneTree signals.

ENet’s purpose is to provide a relatively thin, simple and robust network communication layer on top of UDP (User Datagram Protocol).

Note: ENet only uses UDP, not TCP. When forwarding the server port to make your server accessible on the public Internet, you only need to forward the server port in UDP. You can use the UPNP class to try to forward the server port automatically when starting the server.

Tutorials

• High-level multiplayer

• http://enet.bespin.org/usergroup0.html

Properties

Methods

Enumerations

enum CompressionMode:

• COMPRESS_NONE = 0 —- No compression. This uses the most bandwidth, but has the upside of requiring the fewest CPU resources. This option may also be used to make network debugging using tools like Wireshark easier.

• COMPRESS_RANGE_CODER = 1 —- ENet’s built-in range encoding. Works well on small packets, but is not the most efficient algorithm on packets larger than 4 KB.

• COMPRESS_FASTLZ = 2 —- FastLZ compression. This option uses less CPU resources compared to COMPRESS_ZLIB, at the expense of using more bandwidth.

• COMPRESS_ZLIB = 3 —- Zlib compression. This option uses less bandwidth compared to COMPRESS_FASTLZ, at the expense of using more CPU resources. Note that this algorithm is not very efficient on packets smaller than 4 KB. Therefore, it’s recommended to use other compression algorithms in most cases.

• COMPRESS_ZSTD = 4 —- Zstandard compression.

Property Descriptions

• bool always_ordered

Enforce ordered packets when using NetworkedMultiplayerPeer.TRANSFER_MODE_UNRELIABLE (thus behaving similarly to NetworkedMultiplayerPeer.TRANSFER_MODE_UNRELIABLE_ORDERED). This is the only way to use ordering with the RPC system.

• int channel_count

The number of channels to be used by ENet. Channels are used to separate different kinds of data. In reliable or ordered mode, for example, the packet delivery order is ensured on a per-channel basis. This is done to combat latency and reduces ordering restrictions on packets. The delivery status of a packet in one channel won’t stall the delivery of other packets in another channel.

• CompressionMode compression_mode

The compression method used for network packets. These have different tradeoffs of compression speed versus bandwidth, you may need to test which one works best for your use case if you use compression at all.

Note: Most games’ network design involve sending many small packets frequently (smaller than 4 KB each). If in doubt, it is recommended to keep the default compression algorithm as it works best on these small packets.

Note: compression_mode must be set to the same value on both the server and all its clients. Clients will fail to connect if the compression_mode set on the client differs from the one set on the server. Prior to Godot 3.4, the default compression_mode was COMPRESS_NONE. Nonetheless, mixing engine versions between clients and server is not recommended and not officially supported.

• String dtls_hostname

The hostname used for DTLS verification, to be compared against the “CN” value in the certificate provided by the server.

When set to an empty string, the address parameter passed to create_client is used instead.

• bool dtls_verify

Enable or disable certificate verification when use_dtls is true.

• bool server_relay

Enable or disable the server feature that notifies clients of other peers’ connection/disconnection, and relays messages between them. When this option is false, clients won’t be automatically notified of other peers and won’t be able to send them packets through the server.

• int transfer_channel

Set the default channel to be used to transfer data. By default, this value is -1 which means that ENet will only use 2 channels: one for reliable packets, and one for unreliable packets. The channel 0 is reserved and cannot be used. Setting this member to any value between 0 and channel_count (excluded) will force ENet to use that channel for sending data. See channel_count for more information about ENet channels.

• bool use_dtls

When enabled, the client or server created by this peer, will use PacketPeerDTLS instead of raw UDP sockets for communicating with the remote peer. This will make the communication encrypted with DTLS at the cost of higher resource usage and potentially larger packet size.

Note: When creating a DTLS server, make sure you setup the key/certificate pair via set_dtls_key and set_dtls_certificate. For DTLS clients, have a look at the dtls_verify option, and configure the certificate accordingly via set_dtls_certificate.

Method Descriptions

• void close_connection ( int wait_usec=100 )

Closes the connection. Ignored if no connection is currently established. If this is a server it tries to notify all clients before forcibly disconnecting them. If this is a client it simply closes the connection to the server.

• Error create_client ( String address, int port, int in_bandwidth=0, int out_bandwidth=0, int client_port=0 )

Create client that connects to a server at address using specified port. The given address needs to be either a fully qualified domain name (e.g. "www.example.com") or an IP address in IPv4 or IPv6 format (e.g. "192.168.1.1"). The port is the port the server is listening on. The in_bandwidth and out_bandwidth parameters can be used to limit the incoming and outgoing bandwidth to the given number of bytes per second. The default of 0 means unlimited bandwidth. Note that ENet will strategically drop packets on specific sides of a connection between peers to ensure the peer’s bandwidth is not overwhelmed. The bandwidth parameters also determine the window size of a connection which limits the amount of reliable packets that may be in transit at any given time. Returns @GlobalScope.OK if a client was created, @GlobalScope.ERR_ALREADY_IN_USE if this NetworkedMultiplayerENet instance already has an open connection (in which case you need to call close_connection first) or @GlobalScope.ERR_CANT_CREATE if the client could not be created. If client_port is specified, the client will also listen to the given port; this is useful for some NAT traversal techniques.

• Error create_server ( int port, int max_clients=32, int in_bandwidth=0, int out_bandwidth=0 )

Create server that listens to connections via port. The port needs to be an available, unused port between 0 and 65535. Note that ports below 1024 are privileged and may require elevated permissions depending on the platform. To change the interface the server listens on, use set_bind_ip. The default IP is the wildcard "*", which listens on all available interfaces. max_clients is the maximum number of clients that are allowed at once, any number up to 4095 may be used, although the achievable number of simultaneous clients may be far lower and depends on the application. For additional details on the bandwidth parameters, see create_client. Returns @GlobalScope.OK if a server was created, @GlobalScope.ERR_ALREADY_IN_USE if this NetworkedMultiplayerENet instance already has an open connection (in which case you need to call close_connection first) or @GlobalScope.ERR_CANT_CREATE if the server could not be created.

• void disconnect_peer ( int id, bool now=false )

Disconnect the given peer. If “now” is set to true, the connection will be closed immediately without flushing queued messages.

• int get_last_packet_channel ( ) const

Returns the channel of the last packet fetched via PacketPeer.get_packet.

• int get_packet_channel ( ) const

Returns the channel of the next packet that will be retrieved via PacketPeer.get_packet.

• String get_peer_address ( int id ) const

Returns the IP address of the given peer.

• int get_peer_port ( int id ) const

Returns the remote port of the given peer.

• void set_bind_ip ( String ip )

The IP used when creating a server. This is set to the wildcard "*" by default, which binds to all available interfaces. The given IP needs to be in IPv4 or IPv6 address format, for example: "192.168.1.1".

• void set_dtls_certificate ( X509Certificate certificate )

Configure the X509Certificate to use when use_dtls is true. For servers, you must also setup the CryptoKey via set_dtls_key.

• void set_dtls_key ( CryptoKey key )

Configure the CryptoKey to use when use_dtls is true. Remember to also call set_dtls_certificate to setup your X509Certificate.

• void set_peer_timeout ( int id, int timeout_limit, int timeout_min, int timeout_max )

Sets the timeout parameters for a peer. The timeout parameters control how and when a peer will timeout from a failure to acknowledge reliable traffic. Timeout values are expressed in milliseconds.

The timeout_limit is a factor that, multiplied by a value based on the average round trip time, will determine the timeout limit for a reliable packet. When that limit is reached, the timeout will be doubled, and the peer will be disconnected if that limit has reached timeout_min. The timeout_max parameter, on the other hand, defines a fixed timeout for which any packet must be acknowledged or the peer will be dropped.