make-network-process

make-network-process is a built-in function in `C source code'.

(make-network-process &rest ARGS)

Create and return a network server or client process.

In Emacs, network connections are represented by process objects, so
input and output work as for subprocesses and `delete-process' closes
a network connection. However, a network process has no process id,
it cannot be signaled, and the status codes are different from normal
processes.

Arguments are specified as keyword/argument pairs. The following
arguments are defined:

:name NAME -- NAME is name for process. It is modified if necessary
to make it unique.

:buffer BUFFER -- BUFFER is the buffer (or buffer-name) to associate
with the process. Process output goes at end of that buffer, unless
you specify an output stream or filter function to handle the output.
BUFFER may be also nil, meaning that this process is not associated
with any buffer.

:host HOST -- HOST is name of the host to connect to, or its IP
address. The symbol `local' specifies the local host. If specified
for a server process, it must be a valid name or address for the local
host, and only clients connecting to that address will be accepted.

:service SERVICE -- SERVICE is name of the service desired, or an
integer specifying a port number to connect to. If SERVICE is t,
a random port number is selected for the server. (If Emacs was
compiled with getaddrinfo, a port number can also be specified as a
string, e.g. "80", as well as an integer. This is not portable.)

:type TYPE -- TYPE is the type of connection. The default (nil) is a
stream type connection, `datagram' creates a datagram type connection,
`seqpacket' creates a reliable datagram connection.

:family FAMILY -- FAMILY is the address (and protocol) family for the
service specified by HOST and SERVICE. The default (nil) is to use
whatever address family (IPv4 or IPv6) that is defined for the host
and port number specified by HOST and SERVICE. Other address families
supported are:
local -- for a local (i.e. UNIX) address specified by SERVICE.
ipv4 -- use IPv4 address family only.
ipv6 -- use IPv6 address family only.

:local ADDRESS -- ADDRESS is the local address used for the connection.
This parameter is ignored when opening a client process. When specified
for a server process, the FAMILY, HOST and SERVICE args are ignored.

:remote ADDRESS -- ADDRESS is the remote partner's address for the
connection. This parameter is ignored when opening a stream server
process. For a datagram server process, it specifies the initial
setting of the remote datagram address. When specified for a client
process, the FAMILY, HOST, and SERVICE args are ignored.

The format of ADDRESS depends on the address family:
- An IPv4 address is represented as an vector of integers [A B C D P]
corresponding to numeric IP address A.B.C.D and port number P.
- A local address is represented as a string with the address in the
local address space.
- An "unsupported family" address is represented by a cons (F . AV)
where F is the family number and AV is a vector containing the socket
address data with one element per address data byte. Do not rely on
this format in portable code, as it may depend on implementation
defined constants, data sizes, and data structure alignment.

:coding CODING -- If CODING is a symbol, it specifies the coding
system used for both reading and writing for this process. If CODING
is a cons (DECODING . ENCODING), DECODING is used for reading, and
ENCODING is used for writing.

:nowait BOOL -- If BOOL is non-nil for a stream type client process,
return without waiting for the connection to complete; instead, the
sentinel function will be called with second arg matching "open" (if
successful) or "failed" when the connect completes. Default is to use
a blocking connect (i.e. wait) for stream type connections.

:noquery BOOL -- Query the user unless BOOL is non-nil, and process is
running when Emacs is exited.

:stop BOOL -- Start process in the `stopped' state if BOOL non-nil.
In the stopped state, a server process does not accept new
connections, and a client process does not handle incoming traffic.
The stopped state is cleared by `continue-process' and set by
`stop-process'.

:filter FILTER -- Install FILTER as the process filter.

:filter-multibyte BOOL -- If BOOL is non-nil, strings given to the
process filter are multibyte, otherwise they are unibyte.
If this keyword is not specified, the strings are multibyte if
the default value of `enable-multibyte-characters' is non-nil.

:sentinel SENTINEL -- Install SENTINEL as the process sentinel.

:log LOG -- Install LOG as the server process log function. This
function is called when the server accepts a network connection from a
client. The arguments are SERVER, CLIENT, and MESSAGE, where SERVER
is the server process, CLIENT is the new process for the connection,
and MESSAGE is a string.

:plist PLIST -- Install PLIST as the new process's initial plist.

:server QLEN -- if QLEN is non-nil, create a server process for the
specified FAMILY, SERVICE, and connection type (stream or datagram).
If QLEN is an integer, it is used as the max. length of the server's
pending connection queue (also known as the backlog); the default
queue length is 5. Default is to create a client process.

The following network options can be specified for this connection:

:broadcast BOOL -- Allow send and receive of datagram broadcasts.
:dontroute BOOL -- Only send to directly connected hosts.
:keepalive BOOL -- Send keep-alive messages on network stream.
:linger BOOL or TIMEOUT -- Send queued messages before closing.
:oobinline BOOL -- Place out-of-band data in receive data stream.
:priority INT -- Set protocol defined priority for sent packets.
:reuseaddr BOOL -- Allow reusing a recently used local address
(this is allowed by default for a server process).
:bindtodevice NAME -- bind to interface NAME. Using this may require
special privileges on some systems.

Consult the relevant system programmer's manual pages for more
information on using these options.


A server process will listen for and accept connections from clients.
When a client connection is accepted, a new network process is created
for the connection with the following parameters:

- The client's process name is constructed by concatenating the server
process's NAME and a client identification string.
- If the FILTER argument is non-nil, the client process will not get a
separate process buffer; otherwise, the client's process buffer is a newly
created buffer named after the server process's BUFFER name or process
NAME concatenated with the client identification string.
- The connection type and the process filter and sentinel parameters are
inherited from the server process's TYPE, FILTER and SENTINEL.
- The client process's contact info is set according to the client's
addressing information (typically an IP address and a port number).
- The client process's plist is initialized from the server's plist.

Notice that the FILTER and SENTINEL args are never used directly by
the server process. Also, the BUFFER argument is not used directly by
the server process, but via the optional :log function, accepted (and
failed) connections may be logged in the server process's buffer.

The original argument list, modified with the actual connection
information, is available via the `process-contact' function.