java.net.ServerSocket Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.net;
import java.io.Closeable;
import java.io.IOException;
import java.nio.channels.ServerSocketChannel;
/**
* This class represents a server-side socket that waits for incoming client
* connections. A {@code ServerSocket} handles the requests and sends back an
* appropriate reply. The actual tasks that a server socket must accomplish are
* implemented by an internal {@code SocketImpl} instance.
*/
public class ServerSocket implements Closeable {
/**
* The RI specifies that where the caller doesn't give an explicit backlog,
* the default is 50. The OS disagrees, so we need to explicitly call listen(2).
*/
private static final int DEFAULT_BACKLOG = 50;
private final SocketImpl impl;
/**
* @hide internal use only
*/
public SocketImpl getImpl$() {
return impl;
}
static SocketImplFactory factory;
private boolean isBound;
private boolean isClosed;
/**
* Constructs a new unbound {@code ServerSocket}.
*
* @throws IOException if an error occurs while creating the socket.
*/
public ServerSocket() throws IOException {
this.impl = factory != null ? factory.createSocketImpl()
: new PlainServerSocketImpl();
impl.create(true);
}
/**
* Constructs a new {@code ServerSocket} instance bound to the given {@code port}.
* The backlog is set to 50. If {@code port == 0}, a port will be assigned by the OS.
*
* @throws IOException if an error occurs while creating the socket.
*/
public ServerSocket(int port) throws IOException {
this(port, DEFAULT_BACKLOG, Inet4Address.ANY);
}
/**
* Constructs a new {@code ServerSocket} instance bound to the given {@code port}.
* The backlog is set to {@code backlog}.
* If {@code port == 0}, a port will be assigned by the OS.
*
* @throws IOException if an error occurs while creating the socket.
*/
public ServerSocket(int port, int backlog) throws IOException {
this(port, backlog, Inet4Address.ANY);
}
/**
* Constructs a new {@code ServerSocket} instance bound to the given {@code localAddress}
* and {@code port}. The backlog is set to {@code backlog}.
* If {@code localAddress == null}, the ANY address is used.
* If {@code port == 0}, a port will be assigned by the OS.
*
* @throws IOException if an error occurs while creating the socket.
*/
public ServerSocket(int port, int backlog, InetAddress localAddress) throws IOException {
checkListen(port);
this.impl = factory != null ? factory.createSocketImpl()
: new PlainServerSocketImpl();
InetAddress addr = (localAddress == null) ? Inet4Address.ANY : localAddress;
synchronized (this) {
impl.create(true);
try {
impl.bind(addr, port);
isBound = true;
impl.listen(backlog > 0 ? backlog : DEFAULT_BACKLOG);
} catch (IOException e) {
close();
throw e;
}
}
}
/**
* Waits for an incoming request and blocks until the connection is opened.
* This method returns a socket object representing the just opened
* connection.
*
* @return the connection representing socket.
* @throws IOException
* if an error occurs while accepting a new connection.
*/
public Socket accept() throws IOException {
checkOpen();
if (!isBound()) {
throw new SocketException("Socket is not bound");
}
Socket aSocket = new Socket();
try {
implAccept(aSocket);
} catch (IOException e) {
aSocket.close();
throw e;
}
return aSocket;
}
private void checkListen(int aPort) {
if (aPort < 0 || aPort > 65535) {
throw new IllegalArgumentException("Port out of range: " + aPort);
}
}
/**
* Closes this server socket and its implementation. Any attempt to connect
* to this socket thereafter will fail.
*
* @throws IOException
* if an error occurs while closing this socket.
*/
public void close() throws IOException {
isClosed = true;
impl.close();
}
/**
* Gets the local IP address of this server socket or {@code null} if the
* socket is unbound. This is useful for multihomed hosts.
*
* @return the local address of this server socket.
*/
public InetAddress getInetAddress() {
if (!isBound()) {
return null;
}
return impl.getInetAddress();
}
/**
* Gets the local port of this server socket or {@code -1} if the socket is
* unbound.
*
* @return the local port this server is listening on.
*/
public int getLocalPort() {
if (!isBound()) {
return -1;
}
return impl.getLocalPort();
}
/**
* Gets the socket {@link SocketOptions#SO_TIMEOUT accept timeout}.
*
* @throws IOException
* if the option cannot be retrieved.
*/
public synchronized int getSoTimeout() throws IOException {
checkOpen();
return ((Integer) impl.getOption(SocketOptions.SO_TIMEOUT)).intValue();
}
/**
* Invokes the server socket implementation to accept a connection on the
* given socket {@code aSocket}.
*
* @param aSocket
* the concrete {@code SocketImpl} to accept the connection
* request on.
* @throws IOException
* if the connection cannot be accepted.
*/
protected final void implAccept(Socket aSocket) throws IOException {
synchronized (this) {
impl.accept(aSocket.impl);
aSocket.accepted();
}
}
/**
* Sets the server socket implementation factory of this instance. This
* method may only be invoked with sufficient security privilege and only
* once during the application lifetime.
*
* @param aFactory
* the streaming socket factory to be used for further socket
* instantiations.
* @throws IOException
* if the factory could not be set or is already set.
*/
public static synchronized void setSocketFactory(SocketImplFactory aFactory) throws IOException {
if (factory != null) {
throw new SocketException("Factory already set");
}
factory = aFactory;
}
/**
* Sets the {@link SocketOptions#SO_TIMEOUT accept timeout} in milliseconds for this socket.
* This accept timeout defines the period the socket will block waiting to
* accept a connection before throwing an {@code InterruptedIOException}. The value
* {@code 0} (default) is used to set an infinite timeout. To have effect
* this option must be set before the blocking method was called.
*
* @param timeout the timeout in milliseconds or 0 for no timeout.
* @throws SocketException
* if an error occurs while setting the option.
*/
public synchronized void setSoTimeout(int timeout) throws SocketException {
checkOpen();
if (timeout < 0) {
throw new IllegalArgumentException("timeout < 0");
}
impl.setOption(SocketOptions.SO_TIMEOUT, Integer.valueOf(timeout));
}
/**
* Returns a textual representation of this server socket including the
* address, port and the state. The port field is set to {@code 0} if there
* is no connection to the server socket.
*
* @return the textual socket representation.
*/
@Override
public String toString() {
StringBuilder result = new StringBuilder(64);
result.append("ServerSocket[");
if (!isBound()) {
return result.append("unbound]").toString();
}
return result.append("addr=")
.append(getInetAddress().getHostName()).append("/")
.append(getInetAddress().getHostAddress()).append(
",port=0,localport=")
.append(getLocalPort()).append("]")
.toString();
}
/**
* Binds this server socket to the given local socket address with a maximum
* backlog of 50 unaccepted connections. If the {@code localAddr} is set to
* {@code null} the socket will be bound to an available local address on
* any free port of the system.
*
* @param localAddr
* the local address and port to bind on.
* @throws IllegalArgumentException
* if the {@code SocketAddress} is not supported.
* @throws IOException
* if the socket is already bound or a problem occurs during
* binding.
*/
public void bind(SocketAddress localAddr) throws IOException {
bind(localAddr, DEFAULT_BACKLOG);
}
/**
* Binds this server socket to the given local socket address. If the
* {@code localAddr} is set to {@code null} the socket will be bound to an
* available local address on any free port of the system.
*
* @param localAddr the local machine address and port to bind on.
* @param backlog the maximum number of unaccepted connections. Passing 0 or
* a negative value yields the default backlog of 50.
* @throws IllegalArgumentException if the {@code SocketAddress} is not
* supported.
* @throws IOException if the socket is already bound or a problem occurs
* during binding.
*/
public void bind(SocketAddress localAddr, int backlog) throws IOException {
checkOpen();
if (isBound()) {
throw new BindException("Socket is already bound");
}
int port = 0;
InetAddress addr = Inet4Address.ANY;
if (localAddr != null) {
if (!(localAddr instanceof InetSocketAddress)) {
throw new IllegalArgumentException("Local address not an InetSocketAddress: " +
localAddr.getClass());
}
InetSocketAddress inetAddr = (InetSocketAddress) localAddr;
if ((addr = inetAddr.getAddress()) == null) {
throw new SocketException("Host is unresolved: " + inetAddr.getHostName());
}
port = inetAddr.getPort();
}
synchronized (this) {
try {
impl.bind(addr, port);
isBound = true;
impl.listen(backlog > 0 ? backlog : DEFAULT_BACKLOG);
} catch (IOException e) {
close();
throw e;
}
}
}
/**
* Gets the local socket address of this server socket or {@code null} if
* the socket is unbound. This is useful on multihomed hosts.
*
* @return the local socket address and port this socket is bound to.
*/
public SocketAddress getLocalSocketAddress() {
if (!isBound()) {
return null;
}
return new InetSocketAddress(getInetAddress(), getLocalPort());
}
/**
* Returns whether this server socket is bound to a local address and port
* or not.
*
* @return {@code true} if this socket is bound, {@code false} otherwise.
*/
public boolean isBound() {
return isBound;
}
/**
* Returns whether this server socket is closed or not.
*
* @return {@code true} if this socket is closed, {@code false} otherwise.
*/
public boolean isClosed() {
return isClosed;
}
private void checkOpen() throws SocketException {
if (isClosed()) {
throw new SocketException("Socket is closed");
}
}
/**
* Sets the value for the socket option {@code SocketOptions.SO_REUSEADDR}.
*
* @param reuse
* the socket option setting.
* @throws SocketException
* if an error occurs while setting the option value.
*/
public void setReuseAddress(boolean reuse) throws SocketException {
checkOpen();
impl.setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(reuse));
}
/**
* Gets the value of the socket option {@code SocketOptions.SO_REUSEADDR}.
*
* @return {@code true} if the option is enabled, {@code false} otherwise.
* @throws SocketException
* if an error occurs while reading the option value.
*/
public boolean getReuseAddress() throws SocketException {
checkOpen();
return ((Boolean) impl.getOption(SocketOptions.SO_REUSEADDR)).booleanValue();
}
/**
* Sets this socket's {@link SocketOptions#SO_SNDBUF receive buffer size}.
*/
public void setReceiveBufferSize(int size) throws SocketException {
checkOpen();
if (size < 1) {
throw new IllegalArgumentException("size < 1");
}
impl.setOption(SocketOptions.SO_RCVBUF, Integer.valueOf(size));
}
/**
* Returns this socket's {@link SocketOptions#SO_RCVBUF receive buffer size}.
*/
public int getReceiveBufferSize() throws SocketException {
checkOpen();
return ((Integer) impl.getOption(SocketOptions.SO_RCVBUF)).intValue();
}
/**
* Returns this socket's {@code ServerSocketChannel}, if one exists. A channel is
* available only if this socket wraps a channel. (That is, you can go from a
* channel to a socket and back again, but you can't go from an arbitrary socket to a channel.)
* In practice, this means that the socket must have been created by
* {@link java.nio.channels.ServerSocketChannel#open}.
*/
public ServerSocketChannel getChannel() {
return null;
}
/**
* Sets performance preferences for connection time, latency and bandwidth.
*
* This method does currently nothing.
*
* @param connectionTime
* the value representing the importance of a short connecting
* time.
* @param latency
* the value representing the importance of low latency.
* @param bandwidth
* the value representing the importance of high bandwidth.
*/
public void setPerformancePreferences(int connectionTime, int latency, int bandwidth) {
// Our socket implementation only provide one protocol: TCP/IP, so
// we do nothing for this method
}
}