jdk.nio.channels.DatagramChannel — clojure-interop/java.nio 1.0.5

A selectable channel for datagram-oriented sockets.

A datagram channel is created by invoking one of the open methods of this class. It is not possible to create a channel for an arbitrary, pre-existing datagram socket. A newly-created datagram channel is open but not connected. A datagram channel need not be connected in order for the send and receive methods to be used. A datagram channel may be connected, by invoking its connect method, in order to avoid the overhead of the security checks are otherwise performed as part of every send and receive operation. A datagram channel must be connected in order to use the read and write methods, since those methods do not accept or return socket addresses.

Once connected, a datagram channel remains connected until it is disconnected or closed. Whether or not a datagram channel is connected may be determined by invoking its isConnected method.

Socket options are configured using the setOption method. A datagram channel to an Internet Protocol socket supports the following options:

Option Name
Description


 SO_SNDBUF
 The size of the socket send buffer


 SO_RCVBUF
 The size of the socket receive buffer


 SO_REUSEADDR
 Re-use address


 SO_BROADCAST
 Allow transmission of broadcast datagrams


 IP_TOS
 The Type of Service (ToS) octet in the Internet Protocol (IP) header


 IP_MULTICAST_IF
 The network interface for Internet Protocol (IP) multicast datagrams


 IP_MULTICAST_TTL
 The time-to-live for Internet Protocol (IP) multicast
  datagrams


 IP_MULTICAST_LOOP
 Loopback for Internet Protocol (IP) multicast datagrams

Additional (implementation specific) options may also be supported.

Datagram channels are safe for use by multiple concurrent threads. They support concurrent reading and writing, though at most one thread may be reading and at most one thread may be writing at any given time.

*open clj

(*open)

(*open family)

Opens a datagram channel.

The family parameter is used to specify the ProtocolFamily. If the datagram channel is to be used for IP multicasting then this should correspond to the address type of the multicast groups that this channel will join.

The new channel is created by invoking the openDatagramChannel method of the system-wide default SelectorProvider object. The channel will not be connected.

family - The protocol family - java.net.ProtocolFamily

returns: A new datagram channel - java.nio.channels.DatagramChannel

throws: java.lang.UnsupportedOperationException - If the specified protocol family is not supported. For example, suppose the parameter is specified as StandardProtocolFamily.INET6 but IPv6 is not enabled on the platform.

bind clj

(bind this local)

Description copied from interface: NetworkChannel

local - The address to bind the socket, or null to bind the socket to an automatically assigned socket address - java.net.SocketAddress

returns: This channel - java.nio.channels.DatagramChannel

throws: java.nio.channels.AlreadyBoundException - If the socket is already bound

connect clj

(connect this remote)

Connects this channel's socket.

The channel's socket is configured so that it only receives datagrams from, and sends datagrams to, the given remote peer address. Once connected, datagrams may not be received from or sent to any other address. A datagram socket remains connected until it is explicitly disconnected or until it is closed.

This method performs exactly the same security checks as the connect method of the DatagramSocket class. That is, if a security manager has been installed then this method verifies that its checkAccept and checkConnect methods permit datagrams to be received from and sent to, respectively, the given remote address.

This method may be invoked at any time. It will not have any effect on read or write operations that are already in progress at the moment that it is invoked. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if invoking the bind method with a parameter of null.

remote - The remote address to which this channel is to be connected - java.net.SocketAddress

returns: This datagram channel - java.nio.channels.DatagramChannel

throws: java.nio.channels.ClosedChannelException - If this channel is closed

connected? clj

(connected? this)

Tells whether or not this channel's socket is connected.

returns: true if, and only if, this channel's socket is open and connected - boolean

disconnect clj

(disconnect this)

Disconnects this channel's socket.

The channel's socket is configured so that it can receive datagrams from, and sends datagrams to, any remote address so long as the security manager, if installed, permits it.

This method may be invoked at any time. It will not have any effect on read or write operations that are already in progress at the moment that it is invoked.

If this channel's socket is not connected, or if the channel is closed, then invoking this method has no effect.

returns: This datagram channel - java.nio.channels.DatagramChannel

throws: java.io.IOException - If some other I/O error occurs

get-local-address clj

(get-local-address this)

Returns the socket address that this channel's socket is bound to.

Where the channel is bound to an Internet Protocol socket address then the return value from this method is of type InetSocketAddress.

If there is a security manager set, its checkConnect method is called with the local address and -1 as its arguments to see if the operation is allowed. If the operation is not allowed, a SocketAddress representing the loopback address and the local port of the channel's socket is returned.

returns: The SocketAddress that the socket is bound to, or the SocketAddress representing the loopback address if denied by the security manager, or null if the channel's socket is not bound - java.net.SocketAddress

throws: java.nio.channels.ClosedChannelException - If the channel is closed

get-remote-address clj

(get-remote-address this)

Returns the remote address to which this channel's socket is connected.

returns: The remote address; null if the channel's socket is not connected - java.net.SocketAddress

throws: java.nio.channels.ClosedChannelException - If the channel is closed

read clj

(read this dst)

(read this dsts offset length)

Reads a datagram from this channel.

This method may only be invoked if this channel's socket is connected, and it only accepts datagrams from the socket's peer. If there are more bytes in the datagram than remain in the given buffers then the remainder of the datagram is silently discarded. Otherwise this method behaves exactly as specified in the ScatteringByteChannel interface.

dsts - The buffers into which bytes are to be transferred - java.nio.ByteBuffer[] offset - The offset within the buffer array of the first buffer into which bytes are to be transferred; must be non-negative and no larger than dsts.length - int length - The maximum number of buffers to be accessed; must be non-negative and no larger than dsts.length - offset - int

returns: The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream - long

throws: java.nio.channels.NotYetConnectedException - If this channel's socket is not connected

receive clj

(receive this dst)

Receives a datagram via this channel.

If a datagram is immediately available, or if this channel is in blocking mode and one eventually becomes available, then the datagram is copied into the given byte buffer and its source address is returned. If this channel is in non-blocking mode and a datagram is not immediately available then this method immediately returns null.

The datagram is transferred into the given byte buffer starting at its current position, as if by a regular read operation. If there are fewer bytes remaining in the buffer than are required to hold the datagram then the remainder of the datagram is silently discarded.

This method performs exactly the same security checks as the receive method of the DatagramSocket class. That is, if the socket is not connected to a specific remote address and a security manager has been installed then for each datagram received this method verifies that the source's address and port number are permitted by the security manager's checkAccept method. The overhead of this security check can be avoided by first connecting the socket via the connect method.

This method may be invoked at any time. If another thread has already initiated a read operation upon this channel, however, then an invocation of this method will block until the first operation is complete. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if invoking the bind method with a parameter of null.

dst - The buffer into which the datagram is to be transferred - java.nio.ByteBuffer

returns: The datagram's source address, or null if this channel is in non-blocking mode and no datagram was immediately available - java.net.SocketAddress

throws: java.nio.channels.ClosedChannelException - If this channel is closed

send clj

(send this src target)

Sends a datagram via this channel.

If this channel is in non-blocking mode and there is sufficient room in the underlying output buffer, or if this channel is in blocking mode and sufficient room becomes available, then the remaining bytes in the given buffer are transmitted as a single datagram to the given target address.

The datagram is transferred from the byte buffer as if by a regular write operation.

This method performs exactly the same security checks as the send method of the DatagramSocket class. That is, if the socket is not connected to a specific remote address and a security manager has been installed then for each datagram sent this method verifies that the target address and port number are permitted by the security manager's checkConnect method. The overhead of this security check can be avoided by first connecting the socket via the connect method.

This method may be invoked at any time. If another thread has already initiated a write operation upon this channel, however, then an invocation of this method will block until the first operation is complete. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if by invoking the bind method with a parameter of null.

src - The buffer containing the datagram to be sent - java.nio.ByteBuffer target - The address to which the datagram is to be sent - java.net.SocketAddress

returns: The number of bytes sent, which will be either the number of bytes that were remaining in the source buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the datagram in the underlying output buffer - int

throws: java.nio.channels.ClosedChannelException - If this channel is closed

set-option clj

(set-option this name value)

Description copied from interface: NetworkChannel

name - The socket option - java.net.SocketOption value - The value of the socket option. A value of null may be a valid value for some socket options. - T

returns: This channel - <T> java.nio.channels.DatagramChannel

throws: java.lang.UnsupportedOperationException - If the socket option is not supported by this channel

socket clj

(socket this)

Retrieves a datagram socket associated with this channel.

The returned object will not declare any public methods that are not declared in the DatagramSocket class.

returns: A datagram socket associated with this channel - java.net.DatagramSocket

valid-ops clj

(valid-ops this)

Returns an operation set identifying this channel's supported operations.

Datagram channels support reading and writing, so this method returns (SelectionKey.OP_READ | SelectionKey.OP_WRITE).

returns: The valid-operation set - int

write clj

(write this src)

(write this srcs offset length)

Writes a datagram to this channel.

This method may only be invoked if this channel's socket is connected, in which case it sends datagrams directly to the socket's peer. Otherwise it behaves exactly as specified in the GatheringByteChannel interface.

srcs - The buffers from which bytes are to be retrieved - java.nio.ByteBuffer[] offset - The offset within the buffer array of the first buffer from which bytes are to be retrieved; must be non-negative and no larger than srcs.length - int length - The maximum number of buffers to be accessed; must be non-negative and no larger than srcs.length - offset - int

returns: The number of bytes sent, which will be either the number of bytes that were remaining in the source buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the datagram in the underlying output buffer - long

throws: java.nio.channels.NotYetConnectedException - If this channel's socket is not connected