A DatagramBased is a networking interface for representing datagram-based communications.
It is a more or less direct mapping of the core parts of the BSD socket API in a portable GObject interface. It is implemented by Socket, which wraps the UNIX socket API on UNIX and winsock2 on Windows.
DatagramBased is entirely platform independent, and is intended to be used alongside higher-level networking APIs such as IOStream.
It uses vectored scatter/gather I/O by default, allowing for many messages to be sent or received in a single call. Where possible,
implementations of the interface should take advantage of vectored I/O to minimise processing or system calls. For example,
Socket uses recvmmsg and sendmmsg where possible. Callers should
take advantage of scatter/gather I/O (the use of multiple buffers per message) to avoid unnecessary copying of data to assemble or
disassemble a message.
Each DatagramBased operation has a timeout parameter which may be negative for blocking behaviour, zero for non-blocking behaviour, or positive for timeout behaviour. A blocking operation blocks until finished or there is an error. A non-blocking operation will return immediately with a g_io_error_would_block error if it cannot make progress. A timeout operation will block until the operation is complete or the timeout expires; if the timeout expires it will return what progress it made, or g_io_error_timed_out if no progress was made. To know when a call would successfully run you can call condition_check or condition_wait. You can also use create_source and attach it to a MainContext to get callbacks when I/O is possible.
When running a non-blocking operation applications should always be able to handle getting a g_io_error_would_block error even when some other function said that I/O was possible. This can easily happen in case of a race condition in the application, but it can also happen for other reasons. For instance, on Windows a socket is always seen as writable until a write returns g_io_error_would_block.
As with Socket, DatagramBaseds can be either connection oriented (for example, SCTP) or connectionless (for example, UDP). DatagramBaseds must be datagram-based, not stream-based. The interface does not cover connection establishment — use methods on the underlying type to establish a connection before sending and receiving data through the DatagramBased API. For connectionless socket types the target/source address is specified or received in each I/O operation.
Like most other APIs in GLib, DatagramBased is not inherently thread safe. To use a DatagramBased concurrently from multiple threads, you must implement your own locking.