A #GDatagramBased 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 #GSocket, which wraps the UNIX socket API on UNIX and winsock2 on Windows.
#GDatagramBased is entirely platform independent, and is intended to be used alongside higher-level networking APIs such as #GIOStream.
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, #GSocket 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 #GDatagramBased 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 g_datagram_based_condition_check() or g_datagram_based_condition_wait(). You can also use g_datagram_based_create_source() and attach it to a #GMainContext 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 #GSocket, #GDatagramBaseds can be either connection oriented (for example, SCTP) or connectionless (for example, UDP). #GDatagramBaseds 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 #GDatagramBased API. For connectionless socket types the target/source address is specified or received in each I/O operation.
Like most other APIs in GLib, #GDatagramBased is not inherently thread safe. To use a #GDatagramBased concurrently from multiple threads, you must implement your own locking.
- #condition_check(condition : GLib::IOCondition) : GLib::IOCondition
- #condition_wait(condition : GLib::IOCondition, timeout : Int64, cancellable : Gio::Cancellable?) : Bool
- #create_source(condition : GLib::IOCondition, cancellable : Gio::Cancellable?) : GLib::Source
- #receive_messages(messages : Enumerable(Gio::InputMessage), flags : Int32, timeout : Int64, cancellable : Gio::Cancellable?) : Int32
- #send_messages(messages : Enumerable(Gio::OutputMessage), flags : Int32, timeout : Int64, cancellable : Gio::Cancellable?) : Int32