# Class SocketPermission

java.lang.Object
java.security.Permission
java.net.SocketPermission

All Implemented Interfaces:
  `Serializable, Guard`

public final class SocketPermission extends Permission implements Serializable
This class represents access to a network via sockets. A SocketPermission consists of a host specification and a set of "actions" specifying ways to connect to that host. The host is specified as

        host = (hostname | IPv4address | iPv6reference) [:portrange]
        portrange = portnumber | -portnumber | portnumber-[portnumber]

The host is expressed as a DNS name, as a numerical IP address, or as "localhost" (for the local machine). The wildcard "*" may be included once in a DNS name host specification. If it is included, it must be in the leftmost position, as in "*.example.com".

The format of the IPv6reference should follow that specified in RFC 2732: Format for Literal IPv6 Addresses in URLs:

        ipv6reference = "[" IPv6address "]"

For example, you can construct a SocketPermission instance as the following:

        String hostAddress = inetaddress.getHostAddress();
        if (inetaddress instanceof Inet6Address) {
            sp = new SocketPermission("[" + hostAddress + "]:" + port, action);
        } else {
            sp = new SocketPermission(hostAddress + ":" + port, action);
        }

or

        String host = url.getHost();
        sp = new SocketPermission(host + ":" + port, action);

The full uncompressed form of an IPv6 literal address is also valid.

The port or portrange is optional. A port specification of the form "N-", where N is a port number, signifies all ports numbered N and above, while a specification of the form "-N" indicates all ports numbered N and below. The special port value `0` refers to the entire ephemeral port range. This is a fixed range of ports a system may use to allocate dynamic ports from. The actual range may be system dependent.

The possible ways to connect to the host are

     accept
     connect
     listen
     resolve

The "listen" action is only meaningful when used with "localhost" and means the ability to bind to a specified port. The "resolve" action is implied when any of the other actions are present. The action "resolve" refers to host/ip name service lookups.

The actions string is converted to lowercase before processing.

API Note:
  This permission cannot be used for controlling access to resources as the Security Manager is no longer supported.
Since:
  1.2
External Specifications
  - RFC 2732: Format for Literal IPv6 Addresses in URL's
See Also:
  - `Permissions`
  - `SocketPermission`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `SocketPermission(String host, String action)`
  Creates a new SocketPermission object with the specified actions.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object obj)`
  Checks two SocketPermission objects for equality.
  `String`
  `getActions()`
  Returns the canonical string representation of the actions.
  `int`
  `hashCode()`
  Returns the hash code value for this object.
  `boolean`
  `implies(Permission p)`
  Checks if this socket permission object "implies" the specified permission.
  `PermissionCollection`
  `newPermissionCollection()`
  Returns a new PermissionCollection object for storing SocketPermission objects.

  ### Methods declared in class Permission

  `checkGuard, getName, toString`

  ### Methods declared in class Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### SocketPermission

    public SocketPermission(String host, String action)
    Creates a new SocketPermission object with the specified actions. The host is expressed as a DNS name, or as a numerical IP address. Optionally, a port or a portrange may be supplied (separated from the DNS name or IP address by a colon).

    To specify the local machine, use "localhost" as the host. Also note: An empty host String ("") is equivalent to "localhost".

    The actions parameter contains a comma-separated list of the actions granted for the specified host (and port(s)). Possible actions are "connect", "listen", "accept", "resolve", or any combination of those. "resolve" is automatically added when any of the other three are specified.

    Examples of SocketPermission instantiation are the following:

           nr = new SocketPermission("www.example.com", "connect");
           nr = new SocketPermission("www.example.com:80", "connect");
           nr = new SocketPermission("*.example.com", "connect");
           nr = new SocketPermission("*.edu", "resolve");
           nr = new SocketPermission("204.160.241.0", "connect");
           nr = new SocketPermission("localhost:1024-65535", "listen");
           nr = new SocketPermission("204.160.241.0:1024-65535", "connect");

    Parameters:
      `host` - the hostname or IP address of the computer, optionally including a colon followed by a port or port range.
      `action` - the action string.
    Throws:
      `NullPointerException` - if any parameters are null
      `IllegalArgumentException` - if the format of `host` is invalid, or if the `action` string is empty, malformed, or contains an action other than the specified possible actions

- ## Method Details

  - ### implies

    public boolean implies(Permission p)
    Checks if this socket permission object "implies" the specified permission.

    More specifically, this method first ensures that all of the following are true (and returns false if any of them are not):

    - p is an instanceof SocketPermission,
    - p's actions are a proper subset of this object's actions, and
    - p's port range is included in this port range. Note: port range is ignored when p only contains the action, 'resolve'.
    Then `implies` checks each of the following, in order, and for each returns true if the stated condition is true:
    - If this object was initialized with a single IP address and one of p's IP addresses is equal to this object's IP address.
    - If this object is a wildcard domain (such as *.example.com), and p's canonical name (the name without any preceding *) ends with this object's canonical host name. For example, *.example.com implies *.foo.example.com.
    - If this object was not initialized with a single IP address, and one of this object's IP addresses equals one of p's IP addresses.
    - If this canonical name equals p's canonical name.
    If none of the above are true, `implies` returns false.
    Specified by:
      `implies` in class `Permission`
    Parameters:
      `p` - the permission to check against.
    Returns:
      true if the specified permission is implied by this object, false if not.

  - ### equals

    public boolean equals(Object obj)
    Checks two SocketPermission objects for equality.
    Specified by:
      `equals` in class `Permission`
    Parameters:
      `obj` - the object to test for equality with this object.
    Returns:
      true if obj is a SocketPermission, and has the same hostname, port range, and actions as this SocketPermission object. However, port range will be ignored in the comparison if obj only contains the action, 'resolve'.
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    public int hashCode()
    Returns the hash code value for this object.
    Specified by:
      `hashCode` in class `Permission`
    Returns:
      a hash code value for this object.
    See Also:
      - `Object.equals(java.lang.Object)`
      - `System.identityHashCode(Object)`

  - ### getActions

    public String getActions()
    Returns the canonical string representation of the actions. Always returns present actions in the following order: connect, listen, accept, resolve.
    Specified by:
      `getActions` in class `Permission`
    Returns:
      the canonical string representation of the actions.

  - ### newPermissionCollection

    public PermissionCollection newPermissionCollection()
    Returns a new PermissionCollection object for storing SocketPermission objects.

    SocketPermission objects must be stored in a manner that allows them to be inserted into the collection in any order, but that also enables the PermissionCollection `implies` method to be implemented in an efficient (and consistent) manner.

    Overrides:
      `newPermissionCollection` in class `Permission`
    Returns:
      a new PermissionCollection object suitable for storing SocketPermissions.