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.
Constructor: |
public ServerSocket() throws IOException {
setImpl();
}
Creates an unbound server socket. Throws:
IOException - IO error when opening the socket.
- exception:
IOException - IO error when opening the socket.
- revised:
1.4 -
|
ServerSocket(SocketImpl impl) {
this.impl = impl;
impl.setServerSocket(this);
}
Package-private constructor to create a ServerSocket associated with
the given SocketImpl. |
public ServerSocket(int port) throws IOException {
this(port, 50, null);
}
Creates a server socket, bound to the specified port. A port number
of 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. Parameters:
port - the port number, or 0 to use a port
number that is automatically allocated.
Throws:
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.
Also see:
- java.net.SocketImpl
- java.net.SocketImplFactory#createSocketImpl()
- java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory)
- SecurityManager#checkListen
- exception:
IOException - if an I/O error occurs when opening the socket.
- exception:
SecurityException -
if a security manager exists and its checkListen
method doesn't allow the operation.
- exception:
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 {
this(port, backlog, null);
}
Creates a server socket and binds it to the specified local port
number, with the specified backlog.
A port number of 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.
Parameters:
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.
Throws:
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.
Also see:
- java.net.SocketImpl
- java.net.SocketImplFactory#createSocketImpl()
- java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory)
- SecurityManager#checkListen
- exception:
IOException - if an I/O error occurs when opening the socket.
- exception:
SecurityException -
if a security manager exists and its checkListen
method doesn't allow the operation.
- exception:
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,
InetAddress bindAddr) throws IOException {
setImpl();
if (port < 0 || port > 0xFFFF)
throw new IllegalArgumentException(
"Port value out of range: " + port);
if (backlog < 1)
backlog = 50;
try {
bind(new InetSocketAddress(bindAddr, port), backlog);
} catch(SecurityException e) {
close();
throw e;
} catch(IOException e) {
close();
throw e;
}
}
Create a server with the specified port, listen backlog, and
local IP address to bind to. The bindAddr argument
can be used on a multi-homed host for a ServerSocket that
will only accept connect requests to one of its addresses.
If bindAddr is null, it will default accepting
connections on any/all local addresses.
The port must be between 0 and 65535, inclusive.
A port number of 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.
Parameters:
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 to
Throws:
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.
IllegalArgumentException - if the port parameter is outside
the specified range of valid port values, which is between
0 and 65535, inclusive.
Also see:
- SocketOptions
- SocketImpl
- SecurityManager#checkListen
- exception:
IllegalArgumentException - if the port parameter is outside
the specified range of valid port values, which is between
0 and 65535, inclusive.
- since:
JDK1.1 -
|
Method from java.net.ServerSocket Detail: |
public Socket accept() throws IOException {
if (isClosed())
throw new SocketException("Socket is closed");
if (!isBound())
throw new SocketException("Socket is not bound yet");
Socket s = new Socket((SocketImpl) null);
implAccept(s);
return s;
}
Listens for a connection to be made to this socket and accepts
it. The method blocks until a connection is made.
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. |
public void bind(SocketAddress endpoint) throws IOException {
bind(endpoint, 50);
}
Binds the 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.
|
public void bind(SocketAddress endpoint,
int backlog) throws IOException {
if (isClosed())
throw new SocketException("Socket is closed");
if (!oldImpl && isBound())
throw new SocketException("Already bound");
if (endpoint == null)
endpoint = new InetSocketAddress(0);
if (!(endpoint instanceof InetSocketAddress))
throw new IllegalArgumentException("Unsupported address type");
InetSocketAddress epoint = (InetSocketAddress) endpoint;
if (epoint.isUnresolved())
throw new SocketException("Unresolved address");
if (backlog < 1)
backlog = 50;
try {
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkListen(epoint.getPort());
getImpl().bind(epoint.getAddress(), epoint.getPort());
getImpl().listen(backlog);
bound = true;
} catch(SecurityException e) {
bound = false;
throw e;
} catch(IOException e) {
bound = false;
throw e;
}
}
Binds the 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. |
public void close() throws IOException {
synchronized(closeLock) {
if (isClosed())
return;
if (created)
impl.close();
closed = true;
}
}
|
void createImpl() throws SocketException {
if (impl == null)
setImpl();
try {
impl.create(true);
created = true;
} catch (IOException e) {
throw new SocketException(e.getMessage());
}
}
Creates the socket implementation. |
public ServerSocketChannel getChannel() {
return null;
}
|
SocketImpl getImpl() throws SocketException {
if (!created)
createImpl();
return impl;
}
Get the SocketImpl attached to this socket, creating
it if necessary. |
public InetAddress getInetAddress() {
if (!isBound())
return null;
try {
return getImpl().getInetAddress();
} catch (SocketException e) {
// nothing
// If we're bound, the impl has been created
// so we shouldn't get here
}
return null;
}
Returns the local address of this server socket.
If the socket was bound prior to being closed ,
then this method will continue to return the local address
after the socket is closed. |
public int getLocalPort() {
if (!isBound())
return -1;
try {
return getImpl().getLocalPort();
} catch (SocketException e) {
// nothing
// If we're bound, the impl has been created
// so we shouldn't get here
}
return -1;
}
Returns the port number on which this socket is listening.
If the socket was bound prior to being closed ,
then this method will continue to return the port number
after the socket is closed. |
public SocketAddress getLocalSocketAddress() {
if (!isBound())
return null;
return new InetSocketAddress(getInetAddress(), getLocalPort());
}
Returns the address of the endpoint this socket is bound to, or
null if it is not bound yet.
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. |
public synchronized int getReceiveBufferSize() throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
int result = 0;
Object o = getImpl().getOption(SocketOptions.SO_RCVBUF);
if (o instanceof Integer) {
result = ((Integer)o).intValue();
}
return result;
}
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.
Note, the value actually set in the accepted socket is determined by
calling Socket#getReceiveBufferSize() . |
public boolean getReuseAddress() throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
return ((Boolean) (getImpl().getOption(SocketOptions.SO_REUSEADDR))).booleanValue();
}
Tests if SO_REUSEADDR is enabled. |
public synchronized int getSoTimeout() throws IOException {
if (isClosed())
throw new SocketException("Socket is closed");
Object o = getImpl().getOption(SocketOptions.SO_TIMEOUT);
/* extra type safety */
if (o instanceof Integer) {
return ((Integer) o).intValue();
} else {
return 0;
}
}
Retrieve setting for SO_TIMEOUT. 0 returns implies that the
option is disabled (i.e., timeout of infinity). |
protected final void implAccept(Socket s) throws IOException {
SocketImpl si = null;
try {
if (s.impl == null)
s.setImpl();
else {
s.impl.reset();
}
si = s.impl;
s.impl = null;
si.address = new InetAddress();
si.fd = new FileDescriptor();
getImpl().accept(si);
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccept(si.getInetAddress().getHostAddress(),
si.getPort());
}
} catch (IOException e) {
if (si != null)
si.reset();
s.impl = si;
throw e;
} catch (SecurityException e) {
if (si != null)
si.reset();
s.impl = si;
throw e;
}
s.impl = si;
s.postAccept();
}
Subclasses of ServerSocket use this method to override accept()
to return their own subclass of socket. So a FooServerSocket
will typically hand this method an empty FooSocket. On
return from implAccept the FooSocket will be connected to a client. |
public boolean isBound() {
// Before 1.3 ServerSockets were always bound during creation
return bound || oldImpl;
}
Returns the binding state of the ServerSocket. |
public boolean isClosed() {
synchronized(closeLock) {
return closed;
}
}
Returns the closed state of the ServerSocket. |
void setBound() {
bound = true;
}
|
void setCreated() {
created = true;
}
|
public void setPerformancePreferences(int connectionTime,
int latency,
int bandwidth) {
/* Not implemented yet */
}
Sets performance preferences for this ServerSocket.
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. |
public synchronized void setReceiveBufferSize(int size) throws SocketException {
if (!(size > 0)) {
throw new IllegalArgumentException("negative receive size");
}
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_RCVBUF, new Integer(size));
}
Sets a default proposed value for the 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. |
public void setReuseAddress(boolean on) throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
}
Enable/disable the 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. |
public synchronized void setSoTimeout(int timeout) throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
}
Enable/disable 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. |
public static synchronized void setSocketFactory(SocketImplFactory fac) throws IOException {
if (factory != null) {
throw new SocketException("factory already defined");
}
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkSetFactory();
}
factory = fac;
}
Sets the server socket implementation factory for the
application. The factory can be specified only once.
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. |
public String toString() {
if (!isBound())
return "ServerSocket[unbound]";
return "ServerSocket[addr=" + impl.getInetAddress() +
",port=" + impl.getPort() +
",localport=" + impl.getLocalPort() + "]";
}
Returns the implementation address and implementation port of
this socket as a String . |