ENet Plugin

Summary:

ENet plugin is a Xojo plugin that adds ENet network protocol to Xojo.

ENet's purpose is to provide a relatively thin, simple and robust network communication layer on top of UDP (User Datagram Protocol). The primary feature it provides is optional reliable, in-order delivery of packets.

ENet omits certain higher level networking features such as authentication, lobbying, server discovery, encryption, or other similar tasks that are particularly application specific so that the library remains flexible, portable, and easily embeddable.

ENet evolved specifically as a UDP networking layer for the multiplayer first person shooter Cube.

Cube necessitated low latency communication 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 behaviour. 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.

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 guarantees 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.

Remarks:

To install ENet plugin for Xojo you have to create a folder called Plugins in the same folder as your Xojo application is located in and drop the ENet plugin into it.

Agreement:

This product is a commercial software, only registered users are allowed to use it.

Einhugur Software will disable all serial numbers found on Internet and all serial numbers of decoded plugins that have illegally been posted on Internet.

Einhugur Software and the author, are in no way responsible for the bugs that might be found in this product. However, Einhugur Software will do its best to fix the bugs. This software is provided by Einhugur software 'as is' without any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for particular purpose. In no event shall Einhugur Software or its developers be liable for any direct, indirect, incidental, special, exemplary or consequential damages (Including, but not limited to, procurement of substitute goods or services; loss of use, data or profits; or business interruption) however caused any on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage.

Officially we only support versions noted above and up to current official (not alpha or beta versions) version of REALbasic at the date of when this plugin is published. We cannot predict what changes might come in future versions of Xojo.

Note that the ENet plugin uses is free software that can be obtained free of charge for any use.

License for the ENet library that is partially used to power this plugin: