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40.17.2 Network Options

The following network options can be specified when you create a network process. Except for :reuseaddr, you can also set or modify these options later, using set-network-process-option.

For a server process, the options specified with make-network-process are not inherited by the client connections, so you will need to set the necessary options for each child connection as it is created.

:bindtodevice device-name

If device-name is a non-empty string identifying a network interface name (see network-interface-list), only handle packets received on that interface. If device-name is nil (the default), handle packets received on any interface.

Using this option may require special privileges on some systems.

:broadcast broadcast-flag

If broadcast-flag is non-nil for a datagram process, the process will receive datagram packet sent to a broadcast address, and be able to send packets to a broadcast address. This is ignored for a stream connection.

:dontroute dontroute-flag

If dontroute-flag is non-nil, the process can only send to hosts on the same network as the local host.

:keepalive keepalive-flag

If keepalive-flag is non-nil for a stream connection, enable exchange of low-level keep-alive messages.

:linger linger-arg

If linger-arg is non-nil, wait for successful transmission of all queued packets on the connection before it is deleted (see delete-process). If linger-arg is an integer, it specifies the maximum time in seconds to wait for queued packets to be sent before closing the connection. The default is nil, which means to discard unsent queued packets when the process is deleted.

:oobinline oobinline-flag

If oobinline-flag is non-nil for a stream connection, receive out-of-band data in the normal data stream. Otherwise, ignore out-of-band data.

:priority priority

Set the priority for packets sent on this connection to the integer priority. The interpretation of this number is protocol specific; such as setting the TOS (type of service) field on IP packets sent on this connection. It may also have system dependent effects, such as selecting a specific output queue on the network interface.

:reuseaddr reuseaddr-flag

If reuseaddr-flag is non-nil (the default) for a stream server process, allow this server to reuse a specific port number (see :service), unless another process on this host is already listening on that port. If reuseaddr-flag is nil, there may be a period of time after the last use of that port (by any process on the host) where it is not possible to make a new server on that port.

Function: set-network-process-option process option value &optional no-error ¶

This function sets or modifies a network option for network process process. The accepted options and values are as for make-network-process. If no-error is non-nil, this function returns nil instead of signaling an error if option is not a supported option. If the function successfully completes, it returns t.

The current setting of an option is available via the process-contact function.