java.lang.Object java.net.ServerSocket
public class ServerSocket
This class implements server sockets. A server socket waits for requests to come in over the network. It performs some operation based on that request, and then possibly returns a result to the requester.
The actual work of the server socket is performed by an instance of the SocketImpl class. An application can change the socket factory that creates the socket implementation to configure itself to create sockets appropriate to the local firewall.
SocketImpl, setSocketFactory(java.net.SocketImplFactory), ServerSocketChannel
ServerSocket()
ServerSocket(int port)
ServerSocket(int port, int backlog)
ServerSocket(int port, int backlog, InetAddress bindAddr)
Socket accept()
void bind(SocketAddress endpoint)
ServerSocket to a specific address (IP address and port number). void bind(SocketAddress endpoint, int backlog)
ServerSocket to a specific address (IP address and port number). void close()
ServerSocketChannel getChannel()
ServerSocketChannel object associated with this socket, if any. InetAddress getInetAddress()
int getLocalPort()
SocketAddress getLocalSocketAddress()
null if it is not bound yet. int getReceiveBufferSize()
boolean getReuseAddress()
int getSoTimeout()
protected void implAccept(Socket s)
boolean isBound()
boolean isClosed()
void setPerformancePreferences(int connectionTime, int latency, int bandwidth)
void setReceiveBufferSize(int size)
void setReuseAddress(boolean on)
static void setSocketFactory(SocketImplFactory fac)
void setSoTimeout(int timeout)
String toString()
String. ServerSocket
public ServerSocket()
throws IOException
IOException - IO error when opening the socket.
public ServerSocket(int port)
throws IOException
0 creates a socket on any free port.
The maximum queue length for incoming connection indications (a request to connect) is set to 50. If a connection indication arrives when the queue is full, the connection is refused.
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 checkListen method is called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException.
port - the port number, or 0 to use any free port.
IOException - if an I/O error occurs when opening the socket.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SocketImpl, SocketImplFactory.createSocketImpl(), setSocketFactory(java.net.SocketImplFactory), SecurityManager.checkListen(int)
public ServerSocket(int port,
int backlog)
throws IOException
0 creates a socket on any free port.
The maximum queue length for incoming connection indications (a request to connect) is set to the backlog parameter. If a connection indication arrives when the queue is full, the connection is refused.
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 checkListen method is called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException.
The backlog argument must be a positive value greater than 0. If the value passed if equal or less than 0, then the default value will be assumed.
port - the specified port, or 0 to use any free port.
backlog - the maximum length of the queue.
IOException - if an I/O error occurs when opening the socket.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SocketImpl, SocketImplFactory.createSocketImpl(), setSocketFactory(java.net.SocketImplFactory), SecurityManager.checkListen(int)
public ServerSocket(int port,
int backlog,
InetAddress bindAddr)
throws IOException
If there is a security manager, this method calls its checkListen method with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException.
The backlog argument must be a positive value greater than 0. If the value passed if equal or less than 0, then the default value will be assumed.
port - the local TCP port
backlog - the listen backlog
bindAddr - the local InetAddress the server will bind to
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
IOException - if an I/O error occurs when opening the socket.
SocketOptions, SocketImpl, SecurityManager.checkListen(int)
public void bind(SocketAddress endpoint)
throws IOException
ServerSocket to a specific address (IP address and port number).
If the address is null, then the system will pick up an ephemeral port and a valid local address to bind the socket.
endpoint - The IP address & port number to bind to.
IOException - if the bind operation fails, or if the socket is already bound.
SecurityException - if a SecurityManager is present and its checkListen method doesn't allow the operation.
IllegalArgumentException - if endpoint is a SocketAddress subclass not supported by this socket
public void bind(SocketAddress endpoint,
int backlog)
throws IOException
ServerSocket to a specific address (IP address and port number).
If the address is null, then the system will pick up an ephemeral port and a valid local address to bind the socket.
The backlog argument must be a positive value greater than 0. If the value passed if equal or less than 0, then the default value will be assumed.
endpoint - The IP address & port number to bind to.
backlog - The listen backlog length.
IOException - if the bind operation fails, or if the socket is already bound.
SecurityException - if a SecurityManager is present and its checkListen method doesn't allow the operation.
IllegalArgumentException - if endpoint is a SocketAddress subclass not supported by this socket
public InetAddress getInetAddress()
null if the socket is unbound.
public int getLocalPort()
public SocketAddress getLocalSocketAddress()
null if it is not bound yet.
SocketAddress representing the local endpoint of this socket, or null if it is not bound yet.
getInetAddress(), getLocalPort(), bind(SocketAddress)
public Socket accept()
throws IOException
A new Socket s is created and, if there is a security manager, the security manager's checkAccept method is called with s.getInetAddress().getHostAddress() and s.getPort() as its arguments to ensure the operation is allowed. This could result in a SecurityException.
IOException - if an I/O error occurs when waiting for a connection.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SocketTimeoutException - if a timeout was previously set with setSoTimeout and the timeout has been reached.
IllegalBlockingModeException - if this socket has an associated channel, the channel is in non-blocking mode, and there is no connection ready to be accepted
SecurityManager.checkAccept(java.lang.String, int)
protected final void implAccept(Socket s)
throws IOException
s - the Socket
IllegalBlockingModeException - if this socket has an associated channel, and the channel is in non-blocking mode
IOException - if an I/O error occurs when waiting for a connection.
public void close()
throws IOException
accept() will throw a SocketException.
If this socket has an associated channel then the channel is closed as well.
IOException - if an I/O error occurs when closing the socket.
public ServerSocketChannel getChannel()
ServerSocketChannel object associated with this socket, if any.
A server socket will have a channel if, and only if, the channel itself was created via the ServerSocketChannel.open method.
public boolean isBound()
public boolean isClosed()
public void setSoTimeout(int timeout)
throws SocketException
timeout - the specified timeout, in milliseconds
SocketException - if there is an error in the underlying protocol, such as a TCP error.
getSoTimeout()
public int getSoTimeout()
throws IOException
IOException - if an I/O error occurs
setSoTimeout(int)
public void setReuseAddress(boolean on)
throws SocketException
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 ServerSocket is created the initial setting of SO_REUSEADDR is not defined. Applications can use getReuseAddress() to determine the initial setting of SO_REUSEADDR.
The behaviour when SO_REUSEADDR is enabled or disabled after a socket is bound (See isBound()) is not defined.
on - whether to enable or disable the socket option
SocketException - if an error occurs enabling or disabling the SO_RESUEADDR socket option, or the socket is closed.
getReuseAddress(), bind(SocketAddress), isBound(), isClosed()
public boolean getReuseAddress()
throws SocketException
boolean indicating whether or not SO_REUSEADDR is enabled.
SocketException - if there is an error in the underlying protocol, such as a TCP error.
setReuseAddress(boolean)
public String toString()
String.
toString in class Object
public static void setSocketFactory(SocketImplFactory fac)
throws IOException
When an application creates a new server 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.
fac - the desired factory.
IOException - if an I/O error occurs when setting the socket factory.
SocketException - if the factory has already been defined.
SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.
SocketImplFactory.createSocketImpl(), SecurityManager.checkSetFactory()
public void setReceiveBufferSize(int size)
throws SocketException
Socket.getReceiveBufferSize() after the socket is returned by accept().
The value of SO_RCVBUF is used both to set the size of the internal socket receive buffer, and to set the size of the TCP receive window that is advertized to the remote peer.
It is possible to change the value subsequently, by calling Socket.setReceiveBufferSize(int). However, if the application wishes to allow a receive window larger than 64K bytes, as defined by RFC1323 then the proposed value must be set in the ServerSocket before it is bound to a local address. This implies, that the ServerSocket must be created with the no-argument constructor, then setReceiveBufferSize() must be called and lastly the ServerSocket is bound to an address by calling bind().
Failure to do this will not cause an error, and the buffer size may be set to the requested value but the TCP receive window in sockets accepted from this ServerSocket will be no larger than 64K bytes.
size - the size to which to set the receive buffer size. This value must be greater than 0.
SocketException - if there is an error in the underlying protocol, such as a TCP error.
IllegalArgumentException - if the value is 0 or is negative.
getReceiveBufferSize()
public int getReceiveBufferSize()
throws SocketException
Note, the value actually set in the accepted socket is determined by calling Socket.getReceiveBufferSize().
SocketException - if there is an error in the underlying protocol, such as a TCP error.
setReceiveBufferSize(int)
public void setPerformancePreferences(int connectionTime,
int latency,
int bandwidth)
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. 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 bound will have no effect. This implies that in order to use this capability requires the socket to be created with the no-argument constructor.
connectionTime - An int expressing the relative importance of a short connection time
latency - An int expressing the relative importance of low latency
bandwidth - An int expressing the relative importance of high bandwidth
Copyright © 2004, 2010 Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
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