Socket

java.lang.Object
- java.net.Socket

All Implemented Interfaces:

AutoCloseable
```
public class Socket
extends Object
implements AutoCloseable
```
This class models a client site socket. A socket is a TCP/IP endpoint for network communications conceptually similar to a file handle.
This class does not actually do any work. Instead, it redirects all of its calls to a socket implementation object which implements the SocketImpl interface. The implementation class is instantiated by factory class that implements the SocketImplFactory interface. A default factory is provided, however the factory may be set by a call to the setSocketImplFactory method. Note that this may only be done once per virtual machine. If a subsequent attempt is made to set the factory, a SocketException will be thrown.

Author:

Aaron M. Renn (arenn@urbanophile.com), Per Bothner (bothner@cygnus.com)

Constructor Summary

Constructors
Constructor and Description
`Socket()` Initializes a new instance of `Socket` object without connecting to a remote host.
`Socket(InetAddress address, int port)` Initializes a new instance of `Socket` and connects to the address and port number specified as arguments.
`Socket(InetAddress address, int port, InetAddress localAddr, int localPort)` Initializes a new instance of `Socket` and connects to the address and port number specified as arguments, plus binds to the specified local address and port.
`Socket(String host, int port)` Initializes a new instance of `Socket` and connects to the hostname and port specified as arguments.
`Socket(String host, int port, InetAddress localAddr, int localPort)` Initializes a new instance of `Socket` that connects to the named host on the specified port and binds to the specified local address and port.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`available()` Returns the number of bytes that the caller can read from this socket without blocking.
`void`	`bind(SocketAddress bindpoint)` Binds the socket to the given local address/port
`void`	`close()` Closes the socket.
`void`	`connect(SocketAddress endpoint)` Connects the socket with a remote address.
`void`	`connect(SocketAddress endpoint, int timeout)` Connects the socket with a remote address.
`void`	`flush()`
`InetAddress`	`getInetAddress()` Returns the address of the remote end of the socket.
`InputStream`	`getInputStream()` Returns an InputStream for reading from this socket.
`boolean`	`getKeepAlive()` This method returns the value of the socket level socket option SO_KEEPALIVE.
`InetAddress`	`getLocalAddress()` Returns the local address to which this socket is bound.
`int`	`getLocalPort()` Returns the local port number to which this socket is bound.
`SocketAddress`	`getLocalSocketAddress()` Returns local socket address.
`boolean`	`getOOBInline()` Returns the current setting of the SO_OOBINLINE option for this socket
`OutputStream`	`getOutputStream()` Returns an OutputStream for writing to this socket.
`int`	`getPort()` Returns the port number of the remote end of the socket connection.
`int`	`getReceiveBufferSize()` This method returns the value of the system level socket option SO_RCVBUF, which is used by the operating system to tune buffer sizes for data transfers.
`SocketAddress`	`getRemoteSocketAddress()` Returns the remote socket address.
`boolean`	`getReuseAddress()` Checks if the SO_REUSEADDR option is enabled
`int`	`getSendBufferSize()` This method returns the value of the system level socket option SO_SNDBUF, which is used by the operating system to tune buffer sizes for data transfers.
`int`	`getSoLinger()` Returns the value of the SO_LINGER option on the socket.
`int`	`getSoTimeout()` Returns the value of the SO_TIMEOUT option on the socket.
`boolean`	`getTcpNoDelay()` Tests whether or not the TCP_NODELAY option is set on the socket.
`int`	`getTrafficClass()` Returns the current traffic class
`boolean`	`isBound()` Checks if the socket is already bound.
`boolean`	`isClosed()` Checks if the socket is closed.
`boolean`	`isConnected()` Checks if the socket is connected
`boolean`	`isInputShutdown()` Checks if the socket's input stream is shutdown
`boolean`	`isOutputShutdown()` Checks if the socket's output stream is shutdown
`int`	`read()` Reads the next byte of data and returns it as an int.
`int`	`read(byte[] buf, int offset, int len)` Reads up to len bytes of data into the caller supplied buffer starting at offset bytes from the start of the buffer
`void`	`sendUrgentData(int data)` Sends urgent data through the socket
`void`	`setKeepAlive(boolean on)` This method sets the value for the socket level socket option SO_KEEPALIVE.
`void`	`setOOBInline(boolean on)` Enables/disables the SO_OOBINLINE option
`void`	`setReceiveBufferSize(int size)` This method sets the value for the system level socket option SO_RCVBUF to the specified value.
`void`	`setReuseAddress(boolean reuseAddress)` Enables/Disables the SO_REUSEADDR option
`void`	`setSendBufferSize(int size)` This method sets the value for the system level socket option SO_SNDBUF to the specified value.
`void`	`setSoLinger(boolean on, int linger)` Sets the value of the SO_LINGER option on the socket.
`void`	`setSoTimeout(int timeout)` Sets the value of the SO_TIMEOUT option on the socket.
`void`	`setTcpNoDelay(boolean on)` Sets the TCP_NODELAY option on the socket.
`void`	`setTrafficClass(int tc)` Sets the traffic class value
`void`	`shutdownInput()` Closes the input side of the socket stream.
`void`	`shutdownOutput()` Closes the output side of the socket stream.
`String`	`toString()` Converts this `Socket` to a `String`.
`void`	`write(byte[] buf, int offset, int len)` Writes len number of bytes from the array buf to the stream starting at offset bytes into the buffer.
`void`	`write(int b)` Writes a byte (passed in as an int) to the given output stream

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Socket
```
public Socket()
```
    Initializes a new instance of Socket object without connecting to a remote host. This useful for subclasses of socket that might want this behavior.
    
    Since:
    
    1.1
  - Socket
```
public Socket(InetAddress address,
              int port)
       throws IOException
```
    Initializes a new instance of Socket and connects to the address and port number specified as arguments.
    
    Parameters:
    
    address - The address to connect to
    
    port - The port number to connect to
    
    Throws:
    
    IOException - If an error occurs
  - Socket
```
public Socket(InetAddress address,
              int port,
              InetAddress localAddr,
              int localPort)
       throws IOException
```
    Initializes a new instance of Socket and connects to the address and port number specified as arguments, plus binds to the specified local address and port.
    
    Parameters:
    
    address - The remote address to connect to
    
    port - The remote port to connect to
    
    localAddr - The local address to connect to
    
    localPort - The local port to connect to
    
    Throws:
    
    IOException - If an error occurs
    
    Since:
    
    1.1
  - Socket
```
public Socket(String host,
              int port)
       throws UnknownHostException,
              IOException
```
    Initializes a new instance of Socket and connects to the hostname and port specified as arguments.
    
    Parameters:
    
    host - The name of the host to connect to
    
    port - The port number to connect to
    
    Throws:
    
    UnknownHostException - If the hostname cannot be resolved to a network address.
    
    IOException - If an error occurs
  - Socket
```
public Socket(String host,
              int port,
              InetAddress localAddr,
              int localPort)
       throws IOException
```
    Initializes a new instance of Socket that connects to the named host on the specified port and binds to the specified local address and port.
    
    Parameters:
    
    host - The name of the remote host to connect to.
    
    port - The remote port to connect to.
    
    localAddr - The local address to bind to.
    
    localPort - The local port to bind to.
    
    Throws:
    
    IOException - If a connection error occurs.
    
    Since:
    
    1.1
- Method Detail
  - available
```
public int available()
              throws IOException
```
    Returns the number of bytes that the caller can read from this socket without blocking.
    
    Returns:
    
    the number of readable bytes before blocking
    
    Throws:
    
    IOException - if an error occurs
  - bind
```
public void bind(SocketAddress bindpoint)
          throws IOException
```
    Binds the socket to the given local address/port
    
    Parameters:
    
    bindpoint - The address/port to bind to
    
    Throws:
    
    IOException - If an error occurs
    
    IllegalArgumentException - If the address type is not supported
    
    Since:
    
    1.4
  - close
```
public void close()
           throws IOException
```
    Closes the socket.
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    IOException - If an error occurs
  - connect
```
public void connect(SocketAddress endpoint)
             throws IOException
```
    Connects the socket with a remote address.
    
    Parameters:
    
    endpoint - The address to connect to
    
    Throws:
    
    IOException - If an error occurs
    
    IllegalArgumentException - If the addess type is not supported
    
    Since:
    
    1.4
  - connect
```
public void connect(SocketAddress endpoint,
                    int timeout)
             throws IOException
```
    Connects the socket with a remote address. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs.
    
    Parameters:
    
    endpoint - The address to connect to
    
    timeout - The length of the timeout in milliseconds, or 0 to indicate no timeout.
    
    Throws:
    
    IOException - If an error occurs
    
    IllegalArgumentException - If the address type is not supported
    
    SocketTimeoutException - If the timeout is reached
    
    Since:
    
    1.4
  - flush
```
public void flush()
           throws IOException
```
    Throws:
    
    IOException
  - getInetAddress
```
public InetAddress getInetAddress()
```
    Returns the address of the remote end of the socket. If this socket is not connected, then null is returned.
    
    Returns:
    
    The remote address this socket is connected to
  - getInputStream
```
public InputStream getInputStream()
                           throws IOException
```
    Returns an InputStream for reading from this socket.
    
    Returns:
    
    The InputStream object
    
    Throws:
    
    IOException - If an error occurs or Socket is not connected
  - getKeepAlive
```
public boolean getKeepAlive()
                     throws SocketException
```
    This method returns the value of the socket level socket option SO_KEEPALIVE.
    
    Returns:
    
    The setting
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    Since:
    
    1.3
  - getLocalAddress
```
public InetAddress getLocalAddress()
```
    Returns the local address to which this socket is bound. If this socket is not connected, then a wildcard address, for which
    
    Returns:
    
    The local address
    
    Since:
    
    1.1
    
    See Also:
    
    is true, is returned.
  - getLocalPort
```
public int getLocalPort()
```
    Returns the local port number to which this socket is bound. If this socket is not connected, then -1 is returned.
    
    Returns:
    
    The local port
  - getLocalSocketAddress
```
public SocketAddress getLocalSocketAddress()
```
    Returns local socket address.
    
    Returns:
    
    the local socket address, null if not bound
    
    Since:
    
    1.4
  - getOOBInline
```
public boolean getOOBInline()
                     throws SocketException
```
    Returns the current setting of the SO_OOBINLINE option for this socket
    
    Returns:
    
    True if SO_OOBINLINE is set, false otherwise.
    
    Throws:
    
    SocketException - If an error occurs
    
    Since:
    
    1.4
  - getOutputStream
```
public OutputStream getOutputStream()
                             throws IOException
```
    Returns an OutputStream for writing to this socket.
    
    Returns:
    
    The OutputStream object
    
    Throws:
    
    IOException - If an error occurs or Socket is not connected
  - getPort
```
public int getPort()
```
    Returns the port number of the remote end of the socket connection. If this socket is not connected, then 0 is returned.
    
    Returns:
    
    The remote port this socket is connected to
  - getReceiveBufferSize
```
public int getReceiveBufferSize()
                         throws SocketException
```
    This method returns the value of the system level socket option SO_RCVBUF, which is used by the operating system to tune buffer sizes for data transfers.
    
    Returns:
    
    The receive buffer size.
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    Since:
    
    1.2
  - getRemoteSocketAddress
```
public SocketAddress getRemoteSocketAddress()
```
    Returns the remote socket address.
    
    Returns:
    
    the remote socket address, null of not connected
    
    Since:
    
    1.4
  - getReuseAddress
```
public boolean getReuseAddress()
                        throws SocketException
```
    Checks if the SO_REUSEADDR option is enabled
    
    Returns:
    
    True if SO_REUSEADDR is set, false otherwise.
    
    Throws:
    
    SocketException - If an error occurs
    
    Since:
    
    1.4
  - getSendBufferSize
```
public int getSendBufferSize()
                      throws SocketException
```
    This method returns the value of the system level socket option SO_SNDBUF, which is used by the operating system to tune buffer sizes for data transfers.
    
    Returns:
    
    The send buffer size.
    
    Throws:
    
    SocketException - If an error occurs or socket not connected
    
    Since:
    
    1.2
  - getSoLinger
```
public int getSoLinger()
                throws SocketException
```
    Returns the value of the SO_LINGER option on the socket. If the SO_LINGER option is set on a socket and there is still data waiting to be sent when the socket is closed, then the close operation will block until either that data is delivered or until the timeout period expires. This method either returns the timeouts (in hundredths of of a second (platform specific?)) if SO_LINGER is set, or -1 if SO_LINGER is not set.
    
    Returns:
    
    The SO_LINGER timeout in hundreths of a second or -1 if SO_LINGER not set
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    Since:
    
    1.1
  - getSoTimeout
```
public int getSoTimeout()
                 throws SocketException
```
    Returns the value of the SO_TIMEOUT option on the socket. If this value is set, and an read/write is performed that does not complete within the timeout period, a short count is returned (or an EWOULDBLOCK signal would be sent in Unix if no data had been read). A value of 0 for this option implies that there is no timeout (ie, operations will block forever). On systems that have separate read and write timeout values, this method returns the read timeout. This value is in thousandths of a second (implementation specific?).
    
    Returns:
    
    The length of the timeout in thousandth's of a second or 0 if not set
    
    Throws:
    
    SocketException - If an error occurs or Socket not connected
    
    Since:
    
    1.1
  - getTcpNoDelay
```
public boolean getTcpNoDelay()
                      throws SocketException
```
    Tests whether or not the TCP_NODELAY option is set on the socket. Returns true if enabled, false if disabled. When on it disables the Nagle algorithm which means that packets are always send immediatly and never merged together to reduce network trafic.
    
    Returns:
    
    Whether or not TCP_NODELAY is set
    
    Throws:
    
    SocketException - If an error occurs or Socket not connected
    
    Since:
    
    1.1
  - getTrafficClass
```
public int getTrafficClass()
                    throws SocketException
```
    Returns the current traffic class
    
    Returns:
    
    The current traffic class.
    
    Throws:
    
    SocketException - If an error occurs
    
    Since:
    
    1.4
    
    See Also:
    
    setTrafficClass(int tc)
  - isBound
```
public boolean isBound()
```
    Checks if the socket is already bound.
    
    Returns:
    
    True if socket is bound, false otherwise.
    
    Since:
    
    1.4
  - isClosed
```
public boolean isClosed()
```
    Checks if the socket is closed.
    
    Returns:
    
    True if socket is closed, false otherwise.
    
    Since:
    
    1.4
  - isConnected
```
public boolean isConnected()
```
    Checks if the socket is connected
    
    Returns:
    
    True if socket is connected, false otherwise.
    
    Since:
    
    1.4
  - isInputShutdown
```
public boolean isInputShutdown()
```
    Checks if the socket's input stream is shutdown
    
    Returns:
    
    True if input is shut down.
    
    Since:
    
    1.4
  - isOutputShutdown
```
public boolean isOutputShutdown()
```
    Checks if the socket's output stream is shutdown
    
    Returns:
    
    True if output is shut down.
    
    Since:
    
    1.4
  - read
```
public int read()
         throws IOException
```
    Reads the next byte of data and returns it as an int.
    
    Returns:
    
    The byte read (as an int) or -1 if end of stream);
    
    Throws:
    
    IOException - If an error occurs.
  - read
```
public int read(byte[] buf,
                int offset,
                int len)
         throws IOException
```
    Reads up to len bytes of data into the caller supplied buffer starting at offset bytes from the start of the buffer
    
    Parameters:
    
    buf - The buffer
    
    offset - Offset into the buffer to start reading from
    
    len - The number of bytes to read
    
    Returns:
    
    The number of bytes actually read or -1 if end of stream
    
    Throws:
    
    IOException - If an error occurs.
  - sendUrgentData
```
public void sendUrgentData(int data)
                    throws IOException
```
    Sends urgent data through the socket
    
    Parameters:
    
    data - The data to send. Only the lowest eight bits of data are sent
    
    Throws:
    
    IOException - If an error occurs
    
    Since:
    
    1.4
  - setKeepAlive
```
public void setKeepAlive(boolean on)
                  throws SocketException
```
    This method sets the value for the socket level socket option SO_KEEPALIVE.
    
    Parameters:
    
    on - True if SO_KEEPALIVE should be enabled
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    Since:
    
    1.3
  - setOOBInline
```
public void setOOBInline(boolean on)
                  throws SocketException
```
    Enables/disables the SO_OOBINLINE option
    
    Parameters:
    
    on - True if SO_OOBLINE should be enabled
    
    Throws:
    
    SocketException - If an error occurs
    
    Since:
    
    1.4
  - setReceiveBufferSize
```
public void setReceiveBufferSize(int size)
                          throws SocketException
```
    This method sets the value for the system level socket option SO_RCVBUF to the specified value. Note that valid values for this option are specific to a given operating system.
    
    Parameters:
    
    size - The new receive buffer size.
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    IllegalArgumentException - If size is 0 or negative
    
    Since:
    
    1.2
  - setReuseAddress
```
public void setReuseAddress(boolean reuseAddress)
                     throws SocketException
```
    Enables/Disables the SO_REUSEADDR option
    
    Parameters:
    
    reuseAddress - true if SO_REUSEADDR should be enabled, false otherwise
    
    Throws:
    
    SocketException - If an error occurs
    
    Since:
    
    1.4
  - setSendBufferSize
```
public void setSendBufferSize(int size)
                       throws SocketException
```
    This method sets the value for the system level socket option SO_SNDBUF to the specified value. Note that valid values for this option are specific to a given operating system.
    
    Parameters:
    
    size - The new send buffer size.
    
    Throws:
    
    SocketException - If an error occurs or Socket not connected
    
    IllegalArgumentException - If size is 0 or negative
    
    Since:
    
    1.2
  - setSoLinger
```
public void setSoLinger(boolean on,
                        int linger)
                 throws SocketException
```
    Sets the value of the SO_LINGER option on the socket. If the SO_LINGER option is set on a socket and there is still data waiting to be sent when the socket is closed, then the close operation will block until either that data is delivered or until the timeout period expires. The linger interval is specified in hundreths of a second (platform specific?)
    
    Parameters:
    
    on - true to enable SO_LINGER, false to disable
    
    linger - The SO_LINGER timeout in hundreths of a second or -1 if SO_LINGER not set.
    
    Throws:
    
    SocketException - If an error occurs or Socket not connected
    
    IllegalArgumentException - If linger is negative
    
    Since:
    
    1.1
  - setSoTimeout
```
public void setSoTimeout(int timeout)
                  throws SocketException
```
    Sets the value of the SO_TIMEOUT option on the socket. If this value is set, and an read/write is performed that does not complete within the timeout period, a short count is returned (or an EWOULDBLOCK signal would be sent in Unix if no data had been read). A value of 0 for this option implies that there is no timeout (ie, operations will block forever). On systems that have separate read and write timeout values, this method returns the read timeout. This value is in milliseconds.
    
    Parameters:
    
    timeout - The length of the timeout in milliseconds, or 0 to indicate no timeout.
    
    Throws:
    
    SocketException - If an error occurs or Socket not connected
    
    Since:
    
    1.1
  - setTcpNoDelay
```
public void setTcpNoDelay(boolean on)
                   throws SocketException
```
    Sets the TCP_NODELAY option on the socket.
    
    Parameters:
    
    on - true to enable, false to disable
    
    Throws:
    
    SocketException - If an error occurs or Socket is not connected
    
    Since:
    
    1.1
  - setTrafficClass
```
public void setTrafficClass(int tc)
                     throws SocketException
```
    Sets the traffic class value
    
    Parameters:
    
    tc - The traffic class
    
    Throws:
    
    SocketException - If an error occurs
    
    IllegalArgumentException - If tc value is illegal
    
    Since:
    
    1.4
    
    See Also:
    
    getTrafficClass()
  - shutdownInput
```
public void shutdownInput()
                   throws IOException
```
    Closes the input side of the socket stream.
    
    Throws:
    
    IOException - If an error occurs.
    
    Since:
    
    1.3
  - shutdownOutput
```
public void shutdownOutput()
                    throws IOException
```
    Closes the output side of the socket stream.
    
    Throws:
    
    IOException - If an error occurs.
    
    Since:
    
    1.3
  - toString
```
public String toString()
```
    Converts this Socket to a String.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    The String representation of this Socket
  - write
```
public void write(byte[] buf,
                  int offset,
                  int len)
           throws IOException
```
    Writes len number of bytes from the array buf to the stream starting at offset bytes into the buffer.
    
    Parameters:
    
    buf - The buffer
    
    offset - Offset into the buffer to start writing from
    
    len - The number of bytes to write
    
    Throws:
    
    IOException - If an error occurs.
  - write
```
public void write(int b)
           throws IOException
```
    Writes a byte (passed in as an int) to the given output stream
    
    Parameters:
    
    b - The byte to write
    
    Throws:
    
    IOException - If an error occurs

Class Socket

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Socket

Socket

Socket

Socket

Socket

Method Detail

available

bind

close

connect

connect

flush

getInetAddress

getInputStream

getKeepAlive

getLocalAddress

getLocalPort

getLocalSocketAddress

getOOBInline

getOutputStream

getPort

getReceiveBufferSize

getRemoteSocketAddress

getReuseAddress

getSendBufferSize

getSoLinger

getSoTimeout

getTcpNoDelay

getTrafficClass

isBound

isClosed

isConnected

isInputShutdown

isOutputShutdown

read

read

sendUrgentData

setKeepAlive

setOOBInline

setReceiveBufferSize

setReuseAddress

setSendBufferSize

setSoLinger

setSoTimeout

setTcpNoDelay

setTrafficClass

shutdownInput

shutdownOutput

toString

write

write