java.lang.Object java.net.DatagramSocket
public class DatagramSocket
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.
DatagramPacket, DatagramChannel
DatagramSocket()
protected DatagramSocket(DatagramSocketImpl impl)
DatagramSocket(int port)
DatagramSocket(int port, InetAddress laddr)
DatagramSocket(SocketAddress bindaddr)
void bind(SocketAddress addr)
void close()
void connect(InetAddress address, int port)
void connect(SocketAddress addr)
void disconnect()
boolean getBroadcast()
DatagramChannel getChannel()
DatagramChannel object associated with this datagram socket, if any. InetAddress getInetAddress()
InetAddress getLocalAddress()
int getLocalPort()
SocketAddress getLocalSocketAddress()
null if it is not bound yet. int getPort()
int getReceiveBufferSize()
SocketAddress getRemoteSocketAddress()
null if it is unconnected. boolean getReuseAddress()
int getSendBufferSize()
int getSoTimeout()
int getTrafficClass()
boolean isBound()
boolean isClosed()
boolean isConnected()
void receive(DatagramPacket p)
void send(DatagramPacket p)
void setBroadcast(boolean on)
static void setDatagramSocketImplFactory(DatagramSocketImplFactory fac)
void setReceiveBufferSize(int size)
void setReuseAddress(boolean on)
void setSendBufferSize(int size)
void setSoTimeout(int timeout)
void setTrafficClass(int tc)
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait DatagramSocket
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.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SecurityManager.checkListen(int)
protected DatagramSocket(DatagramSocketImpl impl)
impl - an instance of a DatagramSocketImpl the subclass wishes to use on the DatagramSocket.
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.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SecurityManager.checkListen(int)
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.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SecurityManager.checkListen(int)
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 use
laddr - local address to bind
SocketException - if the socket could not be opened, or the socket could not bind to the specified local port.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
SecurityManager.checkListen(int)
public 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.
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
IllegalArgumentException - if addr is a SocketAddress subclass not supported by this socket.
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 socket
port - the remote port for the socket.
IllegalArgumentException - if the address is null, or the port is out of range.
SecurityException - if the caller is not allowed to send datagrams to and receive datagrams from the address and port.
disconnect(), send(java.net.DatagramPacket), receive(java.net.DatagramPacket)
public void connect(SocketAddress addr)
throws SocketException
addr - The remote address.
SocketException - if the connect fails
IllegalArgumentException - if addr is null or addr is a SocketAddress subclass not supported by this socket
connect(java.net.InetAddress, int)
public void disconnect()
connect(java.net.InetAddress, int)
public boolean isBound()
public boolean isConnected()
public InetAddress getInetAddress()
public int getPort()
public SocketAddress getRemoteSocketAddress()
null if it is unconnected.
SocketAddress representing the remote endpoint of this socket, or null if it is not connected yet.
getInetAddress(), getPort(), connect(SocketAddress)
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.
getLocalAddress(), getLocalPort(), bind(SocketAddress)
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.
SecurityException - if a security manager exists and its checkMulticast or checkConnect method doesn't allow the send.
PortUnreachableException - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.
IllegalBlockingModeException - if this socket has an associated channel, and the channel is in non-blocking mode.
DatagramPacket, SecurityManager.checkMulticast(InetAddress), SecurityManager.checkConnect(java.lang.String, int)
public 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.
SocketTimeoutException - if setSoTimeout was previously called and the timeout has expired.
PortUnreachableException - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.
IllegalBlockingModeException - if this socket has an associated channel, and the channel is in non-blocking mode.
DatagramPacket, DatagramSocket
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 operation
SecurityManager.checkConnect(java.lang.String, int)
public int getLocalPort()
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 an UDP error.
getSoTimeout()
public int getSoTimeout()
throws SocketException
SocketException - if there is an error in the underlying protocol, such as an UDP error.
setSoTimeout(int)
public void setSendBufferSize(int size)
throws SocketException
As SO_SNDBUF is a hint, applications that want to verify what size the buffer is should call 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 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.
IllegalArgumentException - if the value is 0 or is negative.
getSendBufferSize()
public int getSendBufferSize()
throws SocketException
SocketException - if there is an error in the underlying protocol, such as an UDP error.
setSendBufferSize(int)
public 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 getReceiveBufferSize().
Increasing SO_RCVBUF may allow the network implementation to buffer multiple packets when packets arrive faster than are being received using 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.
IllegalArgumentException - if the value is 0 or is negative.
getReceiveBufferSize()
public int getReceiveBufferSize()
throws SocketException
SocketException - if there is an error in the underlying protocol, such as an UDP error.
setReceiveBufferSize(int)
public 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 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 bind(SocketAddress).
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 isBound()) is not defined.
on - whether to enable or disable the
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 an UDP error.
setReuseAddress(boolean)
public 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.
getBroadcast()
public 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.
setBroadcast(boolean)
public 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
getTrafficClass()
public int getTrafficClass()
throws SocketException
As the underlying network implementation may ignore the traffic class or type-of-service set using setTrafficClass(int) this method may return a different value than was previously set using the setTrafficClass(int) method on this DatagramSocket.
SocketException - if there is an error obtaining the traffic class or type-of-service value.
setTrafficClass(int)
public void close()
Any thread currently blocked in {#link receive} upon this socket will throw a SocketException.
If this socket has an associated channel then the channel is closed as well.
public boolean isClosed()
public DatagramChannel getChannel()
DatagramChannel object associated with this datagram socket, if any.
A datagram socket will have a channel if, and only if, the channel itself was created via the DatagramChannel.open method.
public static 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.
SocketException - if the factory is already defined.
SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.
DatagramSocketImplFactory.createDatagramSocketImpl(), SecurityManager.checkSetFactory()
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