Package libcore.net

Class RawSocket

java.lang.Object
libcore.net.RawSocket
All Implemented Interfaces:
Closeable, AutoCloseable
public class RawSocket
extends Object
implements Closeable
This class allows raw L2 packets to be sent and received via the specified network interface. The receive-side implementation is restricted to UDP packets for efficiency.

  • Field Summary

    Fields
    Modifier and Type Field Description
    static short ETH_P_ARP
    Ethernet ARP protocol type, part of the L2 header of ARP packets.
    static short ETH_P_IP
    Ethernet IP protocol type, part of the L2 header of IP packets.

  • Constructor Summary

    Constructors
    Constructor Description
    RawSocket​(String interfaceName, short protocolType)
    Creates a socket on the specified interface.

  • Method Summary

    Modifier and Type Method Description
    void close()
    Closes the socket.
    protected void finalize()
    Invoked when the garbage collector has detected that this instance is no longer reachable.
    int read​(byte[] packet, int offset, int byteCount, int destPort, int timeoutMillis)
    Reads a raw packet into the specified buffer, with the specified timeout.
    int write​(byte[] destMac, byte[] packet, int offset, int byteCount)
    Writes a raw packet to the desired interface.

    Methods inherited from class java.lang.Object

    clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • ETH_P_IP

      public static final short ETH_P_IP
      Ethernet IP protocol type, part of the L2 header of IP packets.
      See Also:
      Constant Field Values

    • ETH_P_ARP

      public static final short ETH_P_ARP
      Ethernet ARP protocol type, part of the L2 header of ARP packets.
      See Also:
      Constant Field Values

  • Constructor Details

  • Method Details

    • read

      public int read​(byte[] packet, int offset, int byteCount, int destPort, int timeoutMillis)
      Reads a raw packet into the specified buffer, with the specified timeout. If the destPort is -1, then the IP destination port is not verified, otherwise only packets destined for the specified UDP port are returned. Returns the length actually read. No indication of overflow is signaled. The packet data will start at the IP header (EthernetII dest/source/type headers are removed).

    • write

      public int write​(byte[] destMac, byte[] packet, int offset, int byteCount)
      Writes a raw packet to the desired interface. A L2 header will be added which includes the specified destination address, our source MAC, and the specified protocol type. The caller is responsible for computing correct IP-header and payload checksums.

    • close

      public void close() throws IOException
      Closes the socket. After this method is invoked, subsequent read/write operations will fail.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException

    • finalize

      protected void finalize() throws Throwable
      Description copied from class: Object
      Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

      Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

      If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

      Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

      Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

      Overrides:
      finalize in class Object
      Throws:
      Throwable