Module java.base
Package java.net

# Class StandardSocketOptions

java.lang.Object
java.net.StandardSocketOptions

    public final class StandardSocketOptions
    extends Object

Defines the standard socket options.

The `name` of each socket option defined by this class is its field name.

In this release, the socket options defined here are used by `network` channels in the `channels` package.

Since:
  1.7

## Field Summary

Fields
Modifier and Type | Field | Description
--- | --- | ---
`static SocketOption<NetworkInterface>` | `IP_MULTICAST_IF` | The network interface for Internet Protocol (IP) multicast datagrams.
`static SocketOption<Boolean>` | `IP_MULTICAST_LOOP` | Loopback for Internet Protocol (IP) multicast datagrams.
`static SocketOption<Integer>` | `IP_MULTICAST_TTL` | The time-to-live for Internet Protocol (IP) multicast datagrams.
`static SocketOption<Integer>` | `IP_TOS` | The Type of Service (ToS) octet in the Internet Protocol (IP) header.
`static SocketOption<Boolean>` | `SO_BROADCAST` | Allow transmission of broadcast datagrams.
`static SocketOption<Boolean>` | `SO_KEEPALIVE` | Keep connection alive.
`static SocketOption<Integer>` | `SO_LINGER` | Linger on close if data is present.
`static SocketOption<Integer>` | `SO_RCVBUF` | The size of the socket receive buffer.
`static SocketOption<Boolean>` | `SO_REUSEADDR` | Re-use address.
`static SocketOption<Boolean>` | `SO_REUSEPORT` | Re-use port.
`static SocketOption<Integer>` | `SO_SNDBUF` | The size of the socket send buffer.
`static SocketOption<Boolean>` | `TCP_NODELAY` | Disable the Nagle algorithm.

## Method Summary

### Methods declared in class java.lang.Object

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

## Field Details

### SO_BROADCAST

public static final SocketOption<Boolean> SO_BROADCAST
Allow transmission of broadcast datagrams.

The value of this socket option is a `Boolean` that represents whether the option is enabled or disabled. The option is specific to datagram-oriented sockets sending to `IPv4` broadcast addresses. When the socket option is enabled then the socket can be used to send broadcast datagrams.

The initial value of this socket option is `FALSE`. The socket option may be enabled or disabled at any time. Some operating systems may require that the Java virtual machine be started with implementation specific privileges to enable this option or send broadcast datagrams.

See Also:
  RFC 929: Broadcasting Internet Datagrams, `DatagramSocket.setBroadcast(boolean)`

### SO_KEEPALIVE

public static final SocketOption<Boolean> SO_KEEPALIVE
Keep connection alive.

The value of this socket option is a `Boolean` that represents whether the option is enabled or disabled. When the `SO_KEEPALIVE` option is enabled the operating system may use a keep-alive mechanism to periodically probe the other end of a connection when the connection is otherwise idle. The exact semantics of the keep alive mechanism is system dependent and therefore unspecified.

The initial value of this socket option is `FALSE`. The socket option may be enabled or disabled at any time.

See Also:
  RFC 1122 Requirements for Internet Hosts -- Communication Layers, `Socket.setKeepAlive(boolean)`

### SO_SNDBUF

public static final SocketOption<Integer> SO_SNDBUF
The size of the socket send buffer.

The value of this socket option is an `Integer` that is the size of the socket send buffer in bytes. The socket send buffer is an output buffer used by the networking implementation. It may need to be increased for high-volume connections. The value of the socket option is a hint to the implementation to size the buffer and the actual size may differ. The socket option can be queried to retrieve the actual size.

For datagram-oriented sockets, the size of the send buffer may limit the size of the datagrams that may be sent by the socket. Whether datagrams larger than the buffer size are sent or discarded is system dependent.

The initial/default size of the socket send buffer and the range of allowable values is system dependent although a negative size is not allowed. An attempt to set the socket send buffer to larger than its maximum size causes it to be set to its maximum size.

An implementation allows this socket option to be set before the socket is bound or connected. Whether an implementation allows the socket send buffer to be changed after the socket is bound is system dependent.

See Also:
  `Socket.setSendBufferSize(int)`

### SO_RCVBUF

public static final SocketOption<Integer> SO_RCVBUF
The size of the socket receive buffer.

The value of this socket option is an `Integer` that is the size of the socket receive buffer in bytes. The socket receive buffer is an input buffer used by the networking implementation. It may need to be increased for high-volume connections or decreased to limit the possible backlog of incoming data. The value of the socket option is a hint to the implementation to size the buffer and the actual size may differ.

For datagram-oriented sockets, the size of the receive buffer may limit the size of the datagrams that can be received. Whether datagrams larger than the buffer size can be received is system dependent. Increasing the socket receive buffer may be important for cases where datagrams arrive in bursts faster than they can be processed.

In the case of stream-oriented sockets and the TCP/IP protocol, the size of the socket receive buffer may be used when advertising the size of the TCP receive window to the remote peer.

The initial/default size of the socket receive buffer and the range of allowable values is system dependent although a negative size is not allowed. An attempt to set the socket receive buffer to larger than its maximum size causes it to be set to its maximum size.

An implementation allows this socket option to be set before the socket is bound or connected. Whether an implementation allows the socket receive buffer to be changed after the socket is bound is system dependent.

See Also:
  RFC 1323: TCP Extensions for High Performance, `Socket.setReceiveBufferSize(int)`, `ServerSocket.setReceiveBufferSize(int)`

### SO_REUSEADDR

public static final SocketOption<Boolean> SO_REUSEADDR
Re-use address.

The value of this socket option is a `Boolean` that represents whether the option is enabled or disabled. The exact semantics of this socket option are socket type and system dependent.

In the case of stream-oriented sockets, this socket option will usually determine whether the socket can be bound to a socket address when a previous connection involving that socket address is in the TIME_WAIT state. On implementations where the semantics differ, and the socket option is not required to be enabled in order to bind the socket when a previous connection is in this state, then the implementation may choose to ignore this option.

For datagram-oriented sockets the socket option is used to allow multiple programs bind to the same address. This option should be enabled when the socket is to be used for Internet Protocol (IP) multicasting.

An implementation allows this socket option to be set before the socket is bound or connected. Changing the value of this socket option after the socket is bound has no effect. The default value of this socket option is system dependent.

See Also:
  RFC 793: Transmission Control Protocol, `ServerSocket.setReuseAddress(boolean)`

### SO_REUSEPORT

public static final SocketOption<Boolean> SO_REUSEPORT
Re-use port.

The value of this socket option is a `Boolean` that represents whether the option is enabled or disabled. The exact semantics of this socket option are socket type and system dependent.

In the case of stream-oriented sockets, this socket option usually allows multiple listening sockets to be bound to both same address and same port.

For datagram-oriented sockets the socket option usually allows multiple UDP sockets to be bound to the same address and port.

An implementation allows this socket option to be set before the socket is bound or connected. Changing the value of this socket option after the socket is bound has no effect.

Since:
  9

### SO_LINGER

public static final SocketOption<Integer> SO_LINGER
Linger on close if data is present.

The value of this socket option is an `Integer` that controls the action taken when unsent data is queued on the socket and a method to close the socket is invoked. If the value of the socket option is zero or greater, then it represents a timeout value, in seconds, known as the linger interval. The linger interval is the timeout for the `close` method to block while the operating system attempts to transmit the unsent data or it decides that it is unable to transmit the data. If the value of the socket option is less than zero then the option is disabled. In that case the `close` method does not wait until unsent data is transmitted; if possible the operating system will transmit any unsent data before the connection is closed.

This socket option is intended for use with sockets that are configured in `blocking` mode only. The behavior of the `close` method when this option is enabled on a non-blocking socket is not defined.

The initial value of this socket option is a negative value, meaning that the option is disabled. The option may be enabled, or the linger interval changed, at any time. The maximum value of the linger interval is system dependent. Setting the linger interval to a value that is greater than its maximum value causes the linger interval to be set to its maximum value.

See Also:
  `Socket.setSoLinger(boolean, int)`

### IP_TOS

public static final SocketOption<Integer> IP_TOS
The Type of Service (ToS) octet in the Internet Protocol (IP) header.

The value of this socket option is an `Integer` representing the value of the ToS octet in IP packets sent by sockets to an `IPv4` socket. The interpretation of the ToS octet is network specific and is not defined by this class. Further information on the ToS octet can be found in RFC 1349 and RFC 2474. The value of the socket option is a hint. An implementation may ignore the value, or ignore specific values.

The initial/default value of the TOS field in the ToS octet is implementation specific but will typically be `0`. For datagram-oriented sockets the option may be configured at any time after the socket has been bound. The new value of the octet is used when sending subsequent datagrams. It is system dependent whether this option can be queried or changed prior to binding the socket.

The behavior of this socket option on a stream-oriented socket, or an `IPv6` socket, is not defined in this release.

See Also:
  `DatagramSocket.setTrafficClass(int)`

### IP_MULTICAST_IF

public static final SocketOption<NetworkInterface> IP_MULTICAST_IF
The network interface for Internet Protocol (IP) multicast datagrams.

The value of this socket option is a `NetworkInterface` that represents the outgoing interface for multicast datagrams sent by the datagram-oriented socket. For `IPv6` sockets then it is system dependent whether setting this option also sets the outgoing interface for multicast datagrams sent to IPv4 addresses.

The initial/default value of this socket option may be `null` to indicate that outgoing interface will be selected by the operating system, typically based on the network routing tables. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent.

See Also:
  `MulticastChannel`, `MulticastSocket.setInterface(java.net.InetAddress)`

### IP_MULTICAST_TTL

public static final SocketOption<Integer> IP_MULTICAST_TTL
The time-to-live for Internet Protocol (IP) multicast datagrams.

The value of this socket option is an `Integer` in the range `0 <= value <= 255`. It is used to control the scope of multicast datagrams sent by the datagram-oriented socket. In the case of an `IPv4` socket the option is the time-to-live (TTL) on multicast datagrams sent by the socket. Datagrams with a TTL of zero are not transmitted on the network but may be delivered locally. In the case of an `IPv6` socket the option is the hop limit which is number of hops that the datagram can pass through before expiring on the network. For IPv6 sockets it is system dependent whether the option also sets the time-to-live on multicast datagrams sent to IPv4 addresses.

The initial/default value of the time-to-live setting is typically `1`. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent.

See Also:
  `MulticastChannel`, `MulticastSocket.setTimeToLive(int)`

### IP_MULTICAST_LOOP

public static final SocketOption<Boolean> IP_MULTICAST_LOOP
Loopback for Internet Protocol (IP) multicast datagrams.

The value of this socket option is a `Boolean` that controls the loopback of multicast datagrams. The value of the socket option represents if the option is enabled or disabled.

The exact semantics of this socket options are system dependent. In particular, it is system dependent whether the loopback applies to multicast datagrams sent from the socket or received by the socket. For `IPv6` sockets then it is system dependent whether the option also applies to multicast datagrams sent to IPv4 addresses.

The initial/default value of this socket option is `TRUE`. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent.

See Also:
  `MulticastChannel`, `MulticastSocket.setLoopbackMode(boolean)`

### TCP_NODELAY

public static final SocketOption<Boolean> TCP_NODELAY
Disable the Nagle algorithm.

The value of this socket option is a `Boolean` that represents whether the option is enabled or disabled. The socket option is specific to stream-oriented sockets using the TCP/IP protocol. TCP/IP uses an algorithm known as The Nagle Algorithm to coalesce short segments and improve network efficiency.

The default value of this socket option is `FALSE`. The socket option should only be enabled in cases where it is known that the coalescing impacts performance. The socket option may be enabled at any time. In other words, the Nagle Algorithm can be disabled. Once the option is enabled, it is system dependent whether it can be subsequently disabled. If it cannot, then invoking the `setOption` method to disable the option has no effect.

See Also:
  RFC 1122: Requirements for Internet Hosts -- Communication Layers, `Socket.setTcpNoDelay(boolean)`