Marko

A simple library to do reply and request over UDP. This does either multicast or broadcast to send/receive a message.

Unicast: point-to-point communications, can be UDP or TCP

Multicast: one-to-many (group) communications, this can only be UDP

Features

• Socket modelled after python socket module
  • UDP and UDS
  • blocking/non-blocking
• Publisher/Subscriber/Reply/Request
  • one way: Publisher -> Subscriber
  • bi-directional: Reply <-> Request
  • all messaging uses message_t for data

Usage

This library requires a C++17 compiler and an up to date cmake.

mkdir build
cd build
cmake ..

Messsages

Message are just structs that are packed to remove padding. You want them to be fixed length though. Then they are put into message_t which are really just std::vector<uint8_t> for transmitting.

struct __attribute__((packed)) request_t {
  double a; // 8B
  int b;    // 4B
};

request_t r{1.234,22};
sizeof(r); // 12B
message_t msg = pack<request_t>(r);
sizeof(msg); // 12B
request_t rr = unpack<request_t>(msg);

Addresses

• AF_INET: protocol://ip_address:port
  • protocol: udp
  • ip_address: 1.2.3.4 or * or bc(broadcast)
  • port: 1-65535 or *(any available port)
• AF_UNIX: unix://file_path

std::string udp = "udp://1.2.3.4:6000";
std::string unix = "unix://./file/path.server.udp";

Alternate

• ZeroMQ
• nanomsg-next-gen

Todo

• Include Unix Datagram Protocol with SOCK_DGRAM in pub/sub/reply/request
• Include Transmition Control Protocol with SOCK_STREAM in pub/sub/reply/request
• Include Unix Domain Sockets with SOCK_STREAM in pub/sub/reply/request
• Include Unix Domain Sockets with SOCK_DGRAM in pub/sub/reply/request
• For classes that take msg_size for recv() or recvfrom(), set low water mark to that size so the functions will wait for that amount of data before signalling ready to read
• Enable low watermark (SO_RCVLOWAT) for receiving data based on msg_size, this will force socket to wait for a full message without having to call a receive function again

MIT License

Copyright (c) 2014 Kevin J. Walchko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.