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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/httpuv.R
\name{startServer}
\alias{startServer}
\alias{startPipeServer}
\alias{startPipeServer}
\title{Create an HTTP/WebSocket server}
\usage{
startServer(host, port, app)
startPipeServer(name, mask, app)
}
\arguments{
\item{host}{A string that is a valid IPv4 address that is owned by this
server, or \code{"0.0.0.0"} to listen on all IP addresses.}
\item{port}{A number or integer that indicates the server port that should be
listened on. Note that on most Unix-like systems including Linux and Mac OS
X, port numbers smaller than 1025 require root privileges.}
\item{app}{A collection of functions that define your application. See
Details.}
\item{name}{A string that indicates the path for the domain socket (on
Unix-like systems) or the name of the named pipe (on Windows).}
\item{mask}{If non-\code{NULL} and non-negative, this numeric value is used
to temporarily modify the process's umask while the domain socket is being
created. To ensure that only root can access the domain socket, use
\code{strtoi("777", 8)}; or to allow owner and group read/write access, use
\code{strtoi("117", 8)}. If the value is \code{NULL} then the process's
umask is left unchanged. (This parameter has no effect on Windows.)}
}
\value{
A handle for this server that can be passed to
\code{\link{stopServer}} to shut the server down.
}
\description{
Creates an HTTP/WebSocket server on the specified host and port.
}
\details{
\code{startServer} binds the specified port and listens for
connections on an thread running in the background. This background thread
handles the I/O, and when it receives a HTTP request, it will schedule a
call to the user-defined R functions in \code{app} to handle the request.
This scheduling is done with \code{\link[later]{later}()}. When the R call
stack is empty -- in other words, when an interactive R session is sitting
idle at the command prompt -- R will automatically run the scheduled calls.
However, if the call stack is not empty -- if R is evaluating other R code
-- then the callbacks will not execute until either the call stack is
empty, or the \code{\link[later]{run_now}()} function is called. This
function tells R to execute any callbacks that have been scheduled by
\code{\link[later]{later}()}. The \code{\link{service}()} function is
essentially a wrapper for \code{\link[later]{run_now}()}.
In older versions of httpuv (1.3.5 and below), it did not use a background
thread for I/O, and when this function was called, it did not accept
connections immediately. It was necessary to call \code{\link{service}}
repeatedly in order to actually accept and handle connections.
If the port cannot be bound (most likely due to permissions or because it
is already bound), an error is raised.
The \code{app} parameter is where your application logic will be provided
to the server. This can be a list, environment, or reference class that
contains the following named functions/methods:
\describe{
\item{\code{call(req)}}{Process the given HTTP request, and return an
HTTP response. This method should be implemented in accordance with the
\href{https://github.com/jeffreyhorner/Rook/blob/a5e45f751/README.md}{Rook}
specification.} Note that httpuv augments \code{req} with an additional item,
\code{req$HEADERS}, which is a named character vector of request headers.
\item{\code{onHeaders(req)}}{Optional. Similar to \code{call}, but occurs
when headers are received. Return \code{NULL} to continue normal
processing of the request, or a Rook response to send that response,
stop processing the request, and ask the client to close the connection.
(This can be used to implement upload size limits, for example.)}
\item{\code{onWSOpen(ws)}}{Called back when a WebSocket connection is established.
The given object can be used to be notified when a message is received from
the client, to send messages to the client, etc. See \code{\link{WebSocket}}.}
}
The \code{startPipeServer} variant can be used instead of
\code{startServer} to listen on a Unix domain socket or named pipe rather
than a TCP socket (this is not common).
}
\examples{
\dontrun{
# A very basic application
handle <- startServer("0.0.0.0", 5000,
list(
call = function(req) {
list(
status = 200L,
headers = list(
'Content-Type' = 'text/html'
),
body = "Hello world!"
)
}
)
)
stopServer(handle)
}
}
\seealso{
\code{\link{stopServer}}, \code{\link{runServer}}
}
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