The classes in goby/middleware/io provide input/output to various non-publish/subscribe interfaces, such as serial ports, UDP sockets, etc.

Each one of these classes is a goby::middleware::SimpleThread that can be easily launched and joined using goby::middleware::MultiThreadApplication.

Each publishes and subscribes the goby::middleware::protobuf::IOData message, which is a thin wrapper around a set of bytes.

The groups used to publish incoming data and subscribe to outgoing data, as well as the layer on which to do so, are passed as template parameters.

Serial I/O

Serial (RS-232, RS-485, RS-422) devices are still very common on marine systems. The goby::middleware::io::SerialThread provides the majority of the functionality for reading and writing to these ports (based on Boost ASIO). The only method that must be implemented is async_read(), as each protocol (ASCII or binary) has its own (often ad-hoc) delimiter or framing rules.

All the serial implementations in Goby are currently point-to-point.

Line-based ASCII

goby::middleware::io::SerialThreadLineBased implements SerialThread for line-based serial interfaces (those that are delimited by a byte or set of bytes). These are typically ASCII based protocols, often delimited by end-of-line and/or carriage-return characters.

goby::middleware::io::SerialThreadLineBased can use a regex as the delimiter, allowing for multiple delimiters (as some sensors have been known to use).

MAVLink binary

goby::middleware::io::SerialThreadMAVLink implements SerialThread for the MAVLink binary protocol (over serial).

In addition to the usual publish/subscribe of IOData, this MAVLink class will publish/subscribe mavlink::mavlink_message_t as well.

UDP I/O

User Datagram Protocol (UDP) messages are simple IP messages. Since the inherent protocol is message-based, no delimiter logic is needed here.

Point-to-point

The simplest UDP class is goby::middleware::io::UDPPointToPointThread, which has one receiver endpoint.

One-to-many

Slightly more complicated is the goby::middleware::io::UDPOneToManyThread which can address multiple remote endpoints using the udp_dest field of goby::middleware::protobuf::IOData.

MAVLink binary

goby::middleware::io::UDPThreadMAVLink is nearly the same as goby::middleware::io::SerialThreadMAVLink, but for the UDP transport instead of serial.