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int myServerPort = …;
DatagramSocket socket = new DatagramSocket(myServerPort);
Based on 92 examples
DatagramSocket socket = new DatagramSocket();
Based on 74 examples
public class DatagramSocket extends Object
This class represents a socket for sending and receiving datagram packets.
A datagram socket is the sending or receiving point for a packet delivery service. Each packet sent or received on a datagram socket is individually addressed and routed. Multiple packets sent from one machine to another may be routed differently, and may arrive in any order.
UDP broadcasts sends are always enabled on a DatagramSocket. In order to receive broadcast packets a DatagramSocket should be bound to the wildcard address. In some implementations, broadcast packets may also be received when a DatagramSocket is bound to a more specific address.
Example:
DatagramSocket s = new DatagramSocket(null);
s.bind(new InetSocketAddress(8888));
Which is equivalent to:
DatagramSocket s = new DatagramSocket(8888);
Both cases will create a DatagramSocket able to receive broadcasts on
UDP port 8888.
Constructor Summary | |
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Constructs a datagram socket and binds it to any available port on the local host machine. |
|
protected |
Creates an unbound datagram socket with the specified DatagramSocketImpl. |
DatagramSocket(int port) Constructs a datagram socket and binds it to the specified port on the local host machine. |
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DatagramSocket(int port, InetAddress laddr) Creates a datagram socket, bound to the specified local address. |
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DatagramSocket(SocketAddress bindaddr) Creates a datagram socket, bound to the specified local socket address. |
Method Summary | |
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void |
bind(SocketAddress addr) Binds this DatagramSocket to a specific address & port. |
void |
close() Closes this datagram socket. |
void |
connect(InetAddress address, int port) Connects the socket to a remote address for this socket. |
void |
connect(SocketAddress addr) Connects this socket to a remote socket address (IP address + port number). |
void |
Disconnects the socket. |
boolean |
Tests if SO_BROADCAST is enabled. |
DatagramChannel |
Returns the unique java.nio.channels.DatagramChannel object associated with this datagram socket, if any. |
InetAddress |
Returns the address to which this socket is connected. |
InetAddress |
Gets the local address to which the socket is bound. |
int |
Returns the port number on the local host to which this socket is bound. |
SocketAddress |
Returns the address of the endpoint this socket is bound to, or null if it is not bound yet.
|
int |
getPort() Returns the port for this socket. |
int |
Get value of the SO_RCVBUF option for this DatagramSocket, that is the buffer size used by the platform for input on this DatagramSocket. |
SocketAddress |
Returns the address of the endpoint this socket is connected to, or null if it is unconnected.
|
boolean |
Tests if SO_REUSEADDR is enabled. |
int |
Get value of the SO_SNDBUF option for this DatagramSocket, that is the buffer size used by the platform for output on this DatagramSocket. |
int |
Retrieve setting for SO_TIMEOUT. |
int |
Gets traffic class or type-of-service in the IP datagram header for packets sent from this DatagramSocket. |
boolean |
isBound() Returns the binding state of the socket. |
boolean |
isClosed() Returns whether the socket is closed or not. |
boolean |
Returns the connection state of the socket. |
void |
Receives a datagram packet from this socket. |
void |
Sends a datagram packet from this socket. |
void |
setBroadcast(boolean on) Enable/disable SO_BROADCAST. |
static void |
Sets the datagram socket implementation factory for the application. |
void |
setReceiveBufferSize(int size) Sets the SO_RCVBUF option to the specified value for this DatagramSocket. |
void |
setReuseAddress(boolean on) Enable/disable the SO_REUSEADDR socket option. |
void |
setSendBufferSize(int size) Sets the SO_SNDBUF option to the specified value for this DatagramSocket. |
void |
setSoTimeout(int timeout) Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. |
void |
setTrafficClass(int tc) Sets traffic class or type-of-service octet in the IP datagram header for datagrams sent from this DatagramSocket. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public DatagramSocket() throws SocketException
If there is a security manager,
its checkListen
method is first called
with 0 as its argument to ensure the operation is allowed.
This could result in a SecurityException.
SocketException
- if the socket could not be opened,
or the socket could not bind to the specified local port.protected DatagramSocket(DatagramSocketImpl impl)
impl
- an instance of a DatagramSocketImpl
the subclass wishes to use on the DatagramSocket.public DatagramSocket(int port) throws SocketException
If there is a security manager,
its checkListen
method is first called
with the port
argument
as its argument to ensure the operation is allowed.
This could result in a SecurityException.
port
- port to use.SocketException
- if the socket could not be opened,
or the socket could not bind to the specified local port.public DatagramSocket(int port, InetAddress laddr) throws SocketException
If there is a security manager,
its checkListen
method is first called
with the port
argument
as its argument to ensure the operation is allowed.
This could result in a SecurityException.
port
- local port to useladdr
- local address to bindSocketException
- if the socket could not be opened,
or the socket could not bind to the specified local port.public DatagramSocket(SocketAddress bindaddr) throws SocketException
If, if the address is null
, creates an unbound socket.
If there is a security manager,
its checkListen
method is first called
with the port from the socket address
as its argument to ensure the operation is allowed.
This could result in a SecurityException.
bindaddr
- local socket address to bind, or null
for an unbound socket.SocketException
- if the socket could not be opened,
or the socket could not bind to the specified local port.Method Detail |
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public synchronized void bind(SocketAddress addr) throws SocketException
If the address is null
, then the system will pick up
an ephemeral port and a valid local address to bind the socket.
addr
- The address & port to bind to.SocketException
- if any error happens during the bind, or if the
socket is already bound.public void close()
Any thread currently blocked in {@link #receive} upon this socket will throw a {@link SocketException}.
If this socket has an associated channel then the channel is closed as well.
public void connect(InetAddress address, int port)
If the remote destination to which the socket is connected does not exist, or is otherwise unreachable, and if an ICMP destination unreachable packet has been received for that address, then a subsequent call to send or receive may throw a PortUnreachableException. Note, there is no guarantee that the exception will be thrown.
A caller's permission to send and receive datagrams to a given host and port are checked at connect time. When a socket is connected, receive and send will not perform any security checks on incoming and outgoing packets, other than matching the packet's and the socket's address and port. On a send operation, if the packet's address is set and the packet's address and the socket's address do not match, an IllegalArgumentException will be thrown. A socket connected to a multicast address may only be used to send packets.
address
- the remote address for the socketport
- the remote port for the socket.public void connect(SocketAddress addr) throws SocketException
addr
- The remote address.SocketException
- if the connect failspublic void disconnect()
public synchronized boolean getBroadcast() throws SocketException
boolean
indicating whether or not SO_BROADCAST is enabled.SocketException
- if there is an error
in the underlying protocol, such as an UDP error.public DatagramChannel getChannel()
A datagram socket will have a channel if, and only if, the channel itself was created via the {@link java.nio.channels.DatagramChannel#open DatagramChannel.open} method.
public InetAddress getInetAddress()
public InetAddress getLocalAddress()
If there is a security manager, its
checkConnect
method is first called
with the host address and -1
as its arguments to see if the operation is allowed.
InetAddress
representing any local
address if either the socket is not bound, or
the security manager checkConnect
method does not allow the operationpublic 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.public int getPort()
public synchronized int getReceiveBufferSize() throws SocketException
SocketException
- if there is an error in the underlying protocol, such as an UDP error.public SocketAddress getRemoteSocketAddress()
null
if it is unconnected.
SocketAddress
representing the remote
endpoint of this socket, or null
if it is
not connected yet.public synchronized 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 an UDP error.public synchronized int getSendBufferSize() throws SocketException
SocketException
- if there is an error in
the underlying protocol, such as an UDP error.public synchronized int getSoTimeout() throws SocketException
SocketException
- if there is an error in the underlying protocol, such as an UDP error.public synchronized int getTrafficClass() throws SocketException
As the underlying network implementation may ignore the traffic class or type-of-service set using {@link #setTrafficClass(int)} this method may return a different value than was previously set using the {@link #setTrafficClass(int)} method on this DatagramSocket.
SocketException
- if there is an error obtaining the
traffic class or type-of-service value.public boolean isBound()
public boolean isClosed()
public boolean isConnected()
public synchronized void receive(DatagramPacket p) throws IOException
DatagramPacket
's buffer is filled with
the data received. The datagram packet also contains the sender's
IP address, and the port number on the sender's machine.
This method blocks until a datagram is received. The
length
field of the datagram packet object contains
the length of the received message. If the message is longer than
the packet's length, the message is truncated.
If there is a security manager, a packet cannot be received if the
security manager's checkAccept
method
does not allow it.
p
- the DatagramPacket
into which to place
the incoming data.IOException
- if an I/O error occurs.public void send(DatagramPacket p) throws IOException
DatagramPacket
includes information indicating the
data to be sent, its length, the IP address of the remote host,
and the port number on the remote host.
If there is a security manager, and the socket is not currently
connected to a remote address, this method first performs some
security checks. First, if p.getAddress().isMulticastAddress()
is true, this method calls the
security manager's checkMulticast
method
with p.getAddress()
as its argument.
If the evaluation of that expression is false,
this method instead calls the security manager's
checkConnect
method with arguments
p.getAddress().getHostAddress()
and
p.getPort()
. Each call to a security manager method
could result in a SecurityException if the operation is not allowed.
p
- the DatagramPacket
to be sent.IOException
- if an I/O error occurs.public synchronized void setBroadcast(boolean on) throws SocketException
on
- whether or not to have broadcast turned on.SocketException
- if there is an error
in the underlying protocol, such as an UDP error.public static synchronized void setDatagramSocketImplFactory(DatagramSocketImplFactory fac) throws IOException
When an application creates a new datagram socket, the socket
implementation factory's createDatagramSocketImpl
method is
called to create the actual datagram 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
datagram socket factory.public synchronized void setReceiveBufferSize(int size) throws SocketException
Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should call {@link #getReceiveBufferSize()}.
Increasing SO_RCVBUF may allow the network implementation to buffer multiple packets when packets arrive faster than are being received using {@link #receive(DatagramPacket)}.
Note: It is implementation specific if a packet larger than SO_RCVBUF can be received.
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 an UDP error.public synchronized void setReuseAddress(boolean on) throws SocketException
For UDP sockets it may be necessary to bind more than one socket to the same socket address. This is typically for the purpose of receiving multicast packets (See {@link java.net.MulticastSocket}). The SO_REUSEADDR socket option allows multiple sockets to be bound to the same socket address if the SO_REUSEADDR socket option is enabled prior to binding the socket using {@link #bind(SocketAddress)}.
Note: This functionality is not supported by all existing platforms,
so it is implementation specific whether this option will be ignored
or not. However, if it is not supported then
{@link #getReuseAddress()} will always return false
.
When a DatagramSocket is created the initial setting of SO_REUSEADDR is disabled.
The behaviour when SO_REUSEADDR is enabled or disabled after a socket is bound (See {@link #isBound()}) is not defined.
on
- whether to enable or disable theSocketException
- if an error occurs enabling or
disabling the SO_RESUEADDR socket option,
or the socket is closed.public synchronized void setSendBufferSize(int size) throws SocketException
As SO_SNDBUF is a hint, applications that want to verify what size the buffer is should call {@link #getSendBufferSize()}.
Increasing the buffer size may allow multiple outgoing packets to be queued by the network implementation when the send rate is high.
Note: If {@link #send(DatagramPacket)} is used to send a
DatagramPacket
that is larger than the setting
of SO_SNDBUF then it is implementation specific if the
packet is sent or discarded.
size
- the size to which to set the send buffer
size. This value must be greater than 0.SocketException
- if there is an error
in the underlying protocol, such as an UDP error.public synchronized void setSoTimeout(int timeout) throws SocketException
timeout
- the specified timeout in milliseconds.SocketException
- if there is an error in the underlying protocol, such as an UDP error.public synchronized void setTrafficClass(int tc) throws SocketException
The tc must be in the range 0 <= tc <=
255
or an IllegalArgumentException will be thrown.
Notes:
for Internet Protocol v4 the value consists of an octet with precedence and TOS fields as detailed in RFC 1349. The TOS field is bitset created by bitwise-or'ing values such the following :-
IPTOS_LOWCOST (0x02)
IPTOS_RELIABILITY (0x04)
IPTOS_THROUGHPUT (0x08)
IPTOS_LOWDELAY (0x10)
Setting bits in the precedence field may result in a SocketException indicating that the operation is not permitted.
for Internet Protocol v6 tc
is the value that
would be placed into the sin6_flowinfo field of the IP header.
tc
- an int
value for the bitset.SocketException
- if there is an error setting the
traffic class or type-of-service
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