Java socket on windows

The actual work of the socket is performed by an instance of the SocketImpl class. An application, by changing the socket factory that creates the socket implementation, can configure itself to create sockets appropriate to the local firewall.

Constructor Summary

Constructors

Modifier	Constructor and Description
Socket ()

Socket (InetAddress address, int port, InetAddress localAddr, int localPort) Socket (String host, int port, InetAddress localAddr, int localPort)

Method Summary

All Methods Static Methods Instance Methods Concrete Methods

Modifier and Type	Method and Description
void	bind (SocketAddress bindpoint)

void setPerformancePreferences (int connectionTime, int latency, int bandwidth)

Methods inherited from class java.lang.Object

Constructor Detail

Socket

Socket

If there is a security manager, its checkConnect method is called with the proxy host address and port number as its arguments. This could result in a SecurityException.

Examples:

• Socket s = new Socket(Proxy.NO_PROXY); will create a plain socket ignoring any other proxy configuration.
• Socket s = new Socket(new Proxy(Proxy.Type.SOCKS, new InetSocketAddress(«socks.mydom.com», 1080))); will create a socket connecting through the specified SOCKS proxy server.

Socket

Socket

If the specified host is null it is the equivalent of specifying the address as InetAddress.getByName (null) . In other words, it is equivalent to specifying an address of the loopback interface.

If the application has specified a server socket factory, that factory’s createSocketImpl method is called to create the actual socket implementation. Otherwise a «plain» socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

Socket

If the application has specified a socket factory, that factory’s createSocketImpl method is called to create the actual socket implementation. Otherwise a «plain» socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

Socket

If the specified host is null it is the equivalent of specifying the address as InetAddress.getByName (null) . In other words, it is equivalent to specifying an address of the loopback interface.

A local port number of zero will let the system pick up a free port in the bind operation.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

Socket

If the specified local address is null it is the equivalent of specifying the address as the AnyLocal address (see InetAddress.isAnyLocalAddress () ).

A local port number of zero will let the system pick up a free port in the bind operation.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

Socket

If the specified host is null it is the equivalent of specifying the address as InetAddress.getByName (null) . In other words, it is equivalent to specifying an address of the loopback interface.

If the stream argument is true , this creates a stream socket. If the stream argument is false , it creates a datagram socket.

If the application has specified a server socket factory, that factory’s createSocketImpl method is called to create the actual socket implementation. Otherwise a «plain» socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

If a UDP socket is used, TCP/IP related socket options will not apply.

Socket

If the stream argument is true , this creates a stream socket. If the stream argument is false , it creates a datagram socket.

If the application has specified a server socket factory, that factory’s createSocketImpl method is called to create the actual socket implementation. Otherwise a «plain» socket is created.

If there is a security manager, its checkConnect method is called with host.getHostAddress() and port as its arguments. This could result in a SecurityException.

If UDP socket is used, TCP/IP related socket options will not apply.

Method Detail

connect

connect

If the address is null , then the system will pick up an ephemeral port and a valid local address to bind the socket.

getInetAddress

If the socket was connected prior to being closed , then this method will continue to return the connected address after the socket is closed.

getLocalAddress

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, the loopback address is returned.

getPort

If the socket was connected prior to being closed , then this method will continue to return the connected port number after the socket is closed.

getLocalPort

If the socket was bound prior to being closed , then this method will continue to return the local port number after the socket is closed.

getRemoteSocketAddress

If the socket was connected prior to being closed , then this method will continue to return the connected address after the socket is closed.

getLocalSocketAddress

If a socket bound to an endpoint represented by an InetSocketAddress is closed , then this method will continue to return an InetSocketAddress after the socket is closed. In that case the returned InetSocketAddress ‘s address is the wildcard address and its port is the local port that it was bound to.

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 to which this socket is bound is returned.

getChannel

A socket will have a channel if, and only if, the channel itself was created via the SocketChannel.open or ServerSocketChannel.accept methods.

getInputStream

If this socket has an associated channel then the resulting input stream delegates all of its operations to the channel. If the channel is in non-blocking mode then the input stream’s read operations will throw an IllegalBlockingModeException .

Under abnormal conditions the underlying connection may be broken by the remote host or the network software (for example a connection reset in the case of TCP connections). When a broken connection is detected by the network software the following applies to the returned input stream :-

The network software may discard bytes that are buffered by the socket. Bytes that aren’t discarded by the network software can be read using read .

If there are no bytes buffered on the socket, or all buffered bytes have been consumed by read , then all subsequent calls to read will throw an IOException .

If there are no bytes buffered on the socket, and the socket has not been closed using close , then available will return 0 .

Closing the returned InputStream will close the associated socket.

getOutputStream

If this socket has an associated channel then the resulting output stream delegates all of its operations to the channel. If the channel is in non-blocking mode then the output stream’s write operations will throw an IllegalBlockingModeException .

Closing the returned OutputStream will close the associated socket.

setTcpNoDelay

getTcpNoDelay

setSoLinger

getSoLinger

sendUrgentData

setOOBInline

Note, only limited support is provided for handling incoming urgent data. In particular, no notification of incoming urgent data is provided and there is no capability to distinguish between normal data and urgent data unless provided by a higher level protocol.

getOOBInline

setSoTimeout

getSoTimeout

setSendBufferSize

Because SO_SNDBUF is a hint, applications that want to verify what size the buffers were set to should call getSendBufferSize() .

getSendBufferSize

setReceiveBufferSize

Increasing the receive buffer size can increase the performance of network I/O for high-volume connection, while decreasing it can help reduce the backlog of incoming data.

Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should call getReceiveBufferSize() .

The value of SO_RCVBUF is also used to set the TCP receive window that is advertized to the remote peer. Generally, the window size can be modified at any time when a socket is connected. However, if a receive window larger than 64K is required then this must be requested before the socket is connected to the remote peer. There are two cases to be aware of:

For sockets accepted from a ServerSocket, this must be done by calling ServerSocket.setReceiveBufferSize(int) before the ServerSocket is bound to a local address.

For client sockets, setReceiveBufferSize() must be called before connecting the socket to its remote peer.

getReceiveBufferSize

setKeepAlive

getKeepAlive

setTrafficClass

The tc must be in the range 0 or an IllegalArgumentException will be thrown.

For Internet Protocol v4 the value consists of an integer , the least significant 8 bits of which represent the value of the TOS octet in IP packets sent by the socket. RFC 1349 defines the TOS values as follows:

• IPTOS_LOWCOST (0x02)
• IPTOS_RELIABILITY (0x04)
• IPTOS_THROUGHPUT (0x08)
• IPTOS_LOWDELAY (0x10)

The last low order bit is always ignored as this corresponds to the MBZ (must be zero) bit.

Setting bits in the precedence field may result in a SocketException indicating that the operation is not permitted.

As RFC 1122 section 4.2.4.2 indicates, a compliant TCP implementation should, but is not required to, let application change the TOS field during the lifetime of a connection. So whether the type-of-service field can be changed after the TCP connection has been established depends on the implementation in the underlying platform. Applications should not assume that they can change the TOS field after the connection.

For Internet Protocol v6 tc is the value that would be placed into the sin6_flowinfo field of the IP header.

getTrafficClass

As the underlying network implementation may ignore the traffic class or type-of-service set using setTrafficClass(int) this method may return a different value than was previously set using the setTrafficClass(int) method on this Socket.

setReuseAddress

When a TCP connection is closed the connection may remain in a timeout state for a period of time after the connection is closed (typically known as the TIME_WAIT state or 2MSL wait state). For applications using a well known socket address or port it may not be possible to bind a socket to the required SocketAddress if there is a connection in the timeout state involving the socket address or port.

Enabling SO_REUSEADDR prior to binding the socket using bind(SocketAddress) allows the socket to be bound even though a previous connection is in a timeout state.

When a Socket is created the initial setting of SO_REUSEADDR is disabled.

The behaviour when SO_REUSEADDR is enabled or disabled after a socket is bound (See isBound() ) is not defined.

getReuseAddress

close

Any thread currently blocked in an I/O operation upon this socket will throw a SocketException .

Once a socket has been closed, it is not available for further networking use (i.e. can’t be reconnected or rebound). A new socket needs to be created.

Closing this socket will also close the socket’s InputStream and OutputStream .

If this socket has an associated channel then the channel is closed as well.

shutdownInput

If you read from a socket input stream after invoking this method on the socket, the stream’s available method will return 0, and its read methods will return -1 (end of stream).

shutdownOutput

toString

isConnected

Note: Closing a socket doesn’t clear its connection state, which means this method will return true for a closed socket (see isClosed() ) if it was successfuly connected prior to being closed.

isBound

Note: Closing a socket doesn’t clear its binding state, which means this method will return true for a closed socket (see isClosed() ) if it was successfuly bound prior to being closed.

isClosed

isInputShutdown

isOutputShutdown

setSocketImplFactory

When an application creates a new client socket, the socket implementation factory’s createSocketImpl method is called to create the actual socket implementation.

Passing null to the method is a no-op unless the factory was already set.

If there is a security manager, this method first calls the security manager’s checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

setPerformancePreferences

Sockets use the TCP/IP protocol by default. Some implementations may offer alternative protocols which have different performance characteristics than TCP/IP. This method allows the application to express its own preferences as to how these tradeoffs should be made when the implementation chooses from the available protocols.

Performance preferences are described by three integers whose values indicate the relative importance of short connection time, low latency, and high bandwidth. The absolute values of the integers are irrelevant; in order to choose a protocol the values are simply compared, with larger values indicating stronger preferences. Negative values represent a lower priority than positive values. If the application prefers short connection time over both low latency and high bandwidth, for example, then it could invoke this method with the values (1, 0, 0) . If the application prefers high bandwidth above low latency, and low latency above short connection time, then it could invoke this method with the values (0, 1, 2) .

Invoking this method after this socket has been connected will have no effect.

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