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

A selectable channel for stream-oriented connecting sockets.

A socket 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 socket. A newly-created socket channel is open but not yet connected. An attempt to invoke an I/O operation upon an unconnected channel will cause a NotYetConnectedException to be thrown. A socket channel can be connected by invoking its connect method; once connected, a socket channel remains connected until it is closed. Whether or not a socket channel is connected may be determined by invoking its isConnected method.

Socket channels support non-blocking connection: A socket channel may be created and the process of establishing the link to the remote socket may be initiated via the connect method for later completion by the finishConnect method. Whether or not a connection operation is in progress may be determined by invoking the isConnectionPending method.

Socket channels support asynchronous shutdown, which is similar to the asynchronous close operation specified in the Channel class. If the input side of a socket is shut down by one thread while another thread is blocked in a read operation on the socket's channel, then the read operation in the blocked thread will complete without reading any bytes and will return -1. If the output side of a socket is shut down by one thread while another thread is blocked in a write operation on the socket's channel, then the blocked thread will receive an AsynchronousCloseException.

Socket options are configured using the setOption method. Socket channels support 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_KEEPALIVE
 Keep connection alive


 SO_REUSEADDR
 Re-use address


 SO_LINGER
 Linger on close if data is present (when configured in blocking mode
     only)


 TCP_NODELAY
 Disable the Nagle algorithm

Additional (implementation specific) options may also be supported.

Socket 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. The connect and finishConnect methods are mutually synchronized against each other, and an attempt to initiate a read or write operation while an invocation of one of these methods is in progress will block until that invocation is complete.

*open clj

(*open)

(*open remote)

Opens a socket channel and connects it to a remote address.

This convenience method works as if by invoking the open() method, invoking the connect method upon the resulting socket channel, passing it remote, and then returning that channel.

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

returns: A new, and connected, socket channel - java.nio.channels.SocketChannel

throws: java.nio.channels.AsynchronousCloseException - If another thread closes this channel while the connect operation is in progress

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.SocketChannel

throws: java.nio.channels.ConnectionPendingException - If a non-blocking connect operation is already in progress on this channel

connect clj

(connect this remote)

Connects this channel's socket.

If this channel is in non-blocking mode then an invocation of this method initiates a non-blocking connection operation. If the connection is established immediately, as can happen with a local connection, then this method returns true. Otherwise this method returns false and the connection operation must later be completed by invoking the finishConnect method.

If this channel is in blocking mode then an invocation of this method will block until the connection is established or an I/O error occurs.

This method performs exactly the same security checks as the Socket class. That is, if a security manager has been installed then this method verifies that its checkConnect method permits connecting to the address and port number of the given remote endpoint.

This method may be invoked at any time. If a read or write operation upon this channel is invoked while an invocation of this method is in progress then that operation will first block until this invocation is complete. If a connection attempt is initiated but fails, that is, if an invocation of this method throws a checked exception, then the channel will be closed.

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

returns: true if a connection was established, false if this channel is in non-blocking mode and the connection operation is in progress - boolean

throws: java.nio.channels.UnresolvedAddressException - If the given remote address is not fully resolved

connected? clj

(connected? this)

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

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

connection-pending? clj

(connection-pending? this)

Tells whether or not a connection operation is in progress on this channel.

returns: true if, and only if, a connection operation has been initiated on this channel but not yet completed by invoking the finishConnect method - boolean

finish-connect clj

(finish-connect this)

Finishes the process of connecting a socket channel.

A non-blocking connection operation is initiated by placing a socket channel in non-blocking mode and then invoking its connect method. Once the connection is established, or the attempt has failed, the socket channel will become connectable and this method may be invoked to complete the connection sequence. If the connection operation failed then invoking this method will cause an appropriate IOException to be thrown.

If this channel is already connected then this method will not block and will immediately return true. If this channel is in non-blocking mode then this method will return false if the connection process is not yet complete. If this channel is in blocking mode then this method will block until the connection either completes or fails, and will always either return true or throw a checked exception describing the failure.

This method may be invoked at any time. If a read or write operation upon this channel is invoked while an invocation of this method is in progress then that operation will first block until this invocation is complete. If a connection attempt fails, that is, if an invocation of this method throws a checked exception, then the channel will be closed.

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

throws: java.nio.channels.NoConnectionPendingException - If this channel is not connected and a connection operation has not been initiated

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.

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

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)

Description copied from interface: ScatteringByteChannel

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 is not yet connected

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.SocketChannel

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

shutdown-input clj

(shutdown-input this)

Shutdown the connection for reading without closing the channel.

Once shutdown for reading then further reads on the channel will return -1, the end-of-stream indication. If the input side of the connection is already shutdown then invoking this method has no effect.

returns: The channel - java.nio.channels.SocketChannel

throws: java.nio.channels.NotYetConnectedException - If this channel is not yet connected

shutdown-output clj

(shutdown-output this)

Shutdown the connection for writing without closing the channel.

Once shutdown for writing then further attempts to write to the channel will throw ClosedChannelException. If the output side of the connection is already shutdown then invoking this method has no effect.

returns: The channel - java.nio.channels.SocketChannel

throws: java.nio.channels.NotYetConnectedException - If this channel is not yet connected

socket clj

(socket this)

Retrieves a socket associated with this channel.

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

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

valid-ops clj

(valid-ops this)

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

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

returns: The valid-operation set - int

write clj

(write this src)

(write this srcs offset length)

Description copied from interface: GatheringByteChannel

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 written, possibly zero - long

throws: java.nio.channels.NotYetConnectedException - If this channel is not yet connected