public class ServerSocket extends Object implements Closeable
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.
| Constructor and Description |
|---|
ServerSocket()
Creates an unbound server socket.
|
ServerSocket(int port)
Creates a server socket, bound to the specified port.
|
ServerSocket(int port,
int backlog)
Creates a server socket and binds it to the specified local port number, with the specified backlog.
|
ServerSocket(int port,
int backlog,
InetAddress bindAddr)
Create a server with the specified port, listen backlog, and local IP address to bind to.
|
| Modifier and Type | Method and Description |
|---|---|
Socket |
accept()
Listens for a connection to be made to this socket and accepts it.
|
void |
bind(SocketAddress endpoint)
Binds the
ServerSocket to a specific address (IP address and port number). |
void |
bind(SocketAddress endpoint,
int backlog)
Binds the
ServerSocket to a specific address (IP address and port number). |
void |
close()
Closes this socket.
|
InetAddress |
getInetAddress()
Returns the local address of this server socket.
|
int |
getLocalPort()
Returns the port number on which this socket is listening.
|
SocketAddress |
getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to.
|
int |
getReceiveBufferSize()
Gets the value of the
SO_RCVBUF option for this ServerSocket, that is the
proposed buffer size that will be used for Sockets accepted from this ServerSocket. |
boolean |
getReuseAddress()
Tests if
SO_REUSEADDR is enabled. |
int |
getSoTimeout()
Retrieve setting for
SO_TIMEOUT. |
boolean |
isBound()
Returns the binding state of the ServerSocket.
|
boolean |
isClosed()
Returns the closed state of the ServerSocket.
|
void |
setReceiveBufferSize(int size)
Sets a default proposed value for the
SO_RCVBUF option for sockets accepted from
this ServerSocket. |
void |
setReuseAddress(boolean on)
Enable/disable the
SO_REUSEADDR socket option. |
void |
setSoTimeout(int timeout)
Enable/disable
SO_TIMEOUT with the specified timeout, in milliseconds. |
String |
toString()
Returns the implementation address and implementation port of this socket as a
String. |
public ServerSocket()
throws IOException
IOException - IO error when opening the socket.public ServerSocket(int port)
throws IOException
0 means that the port number is
automatically allocated, typically from an ephemeral port range. This port number can then be retrieved by
calling getLocalPort.
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 a port number that is automatically allocated.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.IllegalArgumentException - if the port parameter is outside the specified range of valid port values, which is between 0 and
65535, inclusive.public ServerSocket(int port,
int backlog)
throws IOException
0 means that the port number is automatically allocated, typically from an ephemeral port
range. This port number can then be retrieved by calling getLocalPort.
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 is the requested maximum number of pending connections on the socket. Its exact
semantics are implementation specific. In particular, an implementation may impose a maximum length or may choose
to ignore the parameter altogther. The value provided should be greater than 0. If it is less than or
equal to 0, then an implementation specific default will be used.
port - the port number, or 0 to use a port number that is automatically allocated.backlog - requested maximum length of the queue of incoming connections.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.IllegalArgumentException - if the port parameter is outside the specified range of valid port values, which is between 0 and
65535, inclusive.public ServerSocket(int port,
int backlog,
@Nullable
InetAddress bindAddr)
throws IOException
0 means that the port number is
automatically allocated, typically from an ephemeral port range. This port number can then be retrieved by
calling getLocalPort.
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 is the requested maximum number of pending connections on the socket. Its exact
semantics are implementation specific. In particular, an implementation may impose a maximum length or may choose
to ignore the parameter altogther. The value provided should be greater than 0. If it is less than or
equal to 0, then an implementation specific default will be used.
port - the port number, or 0 to use a port number that is automatically allocated.backlog - requested maximum length of the queue of incoming connections.bindAddr - the local InetAddress the server will bind toSecurityException - 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.IllegalArgumentException - if the port parameter is outside the specified range of valid port values, which is between 0 and
65535, inclusive.SocketOptionspublic void bind(@Nullable 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 and 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 socketpublic void bind(@Nullable 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 is the requested maximum number of pending connections on the socket. Its exact
semantics are implementation specific. In particular, an implementation may impose a maximum length or may choose
to ignore the parameter altogther. The value provided should be greater than 0. If it is less than or
equal to 0, then an implementation specific default will be used.
endpoint - The IP address and port number to bind to.backlog - requested maximum length of the queue of incoming connections.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@Nullable public InetAddress getInetAddress()
If the socket was bound prior to being closed, then this method will continue to return the local
address after the socket is closed.
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.
null if the socket is unbound.public int getLocalPort()
If the socket was bound prior to being closed, then this method will continue to return the port
number after the socket is closed.
@Nullable public SocketAddress getLocalSocketAddress()
If the socket was bound prior to being closed, then this method will continue to return the
address of the endpoint after the socket is closed.
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.
SocketAddress representing the local endpoint of this socket, or null if the socket 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 checkAccept method doesn't allow the operation.SocketTimeoutException - if a timeout was previously set with setSoTimeout and the timeout has been reached.public void close()
throws IOException
accept() will throw a SocketException.
If this socket has an associated channel then the channel is closed as well.
close in interface Closeableclose in interface AutoCloseableIOException - if an I/O error occurs when closing the socket.public boolean isBound()
public boolean isClosed()
public void setSoTimeout(int timeout)
throws SocketException
SO_TIMEOUT with the specified timeout, in milliseconds. With this
option set to a non-zero timeout, a call to accept() for this ServerSocket will block for only this amount of
time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the ServerSocket is
still valid. The option must be enabled prior to entering the blocking operation to have effect. The
timeout must be > 0. A timeout of zero is interpreted as an infinite timeout.timeout - the specified timeout, in millisecondsSocketException - if there is an error in the underlying protocol, such as a TCP error.getSoTimeout()public int getSoTimeout()
throws IOException
SO_TIMEOUT. 0 returns implies that the option is disabled
(i.e., timeout of infinity).SO_TIMEOUT valueIOException - if an I/O error occurssetSoTimeout(int)public void setReuseAddress(boolean on)
throws SocketException
SO_REUSEADDR socket option.
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 optionSocketException - if an error occurs enabling or disabling the SO_REUSEADDR
socket option, or the socket is closed.getReuseAddress(),
bind(SocketAddress),
isBound(),
isClosed()public boolean getReuseAddress()
throws SocketException
SO_REUSEADDR is enabled.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.
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.
public void setReceiveBufferSize(int size)
throws SocketException
SO_RCVBUF option for sockets accepted from
this ServerSocket. The value actually set in the accepted socket must be determined by calling
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
SO_RCVBUF option for this ServerSocket, that is the
proposed buffer size that will be used for Sockets accepted from this ServerSocket.
Note, the value actually set in the accepted socket is determined by calling
Socket.getReceiveBufferSize().
SO_RCVBUF option for this Socket.SocketException - if there is an error in the underlying protocol, such as a TCP error.setReceiveBufferSize(int)