This is an R WebSocket client library backed by thewebsocketpp C++library. WebSocket I/O is handled on a separate thread from R.
library(websocket)ws<- WebSocket$new("ws://echo.websocket.org/",autoConnect =FALSE)ws$onOpen(function(event) {cat("Connection opened\n")})ws$onMessage(function(event) {cat("Client got msg: ", event$data,"\n")})ws$onClose(function(event) {cat("Client disconnected with code ", event$code," and reason ", event$reason,"\n",sep ="")})ws$onError(function(event) {cat("Client failed to connect: ", event$message,"\n")})ws$connect()(If you’re not writing these commands at a console—for instance, ifyou’re using a WebSocket as part of a Shiny app—you can leave offautoConnect=FALSE andws$connect(). These areonly necessary when the creation of the WebSocket object and theregistering of theonOpen/onMessage/onClose handlersdon’t happen within the same function call, because in those cases theconnection may open and/or messages received before the handlers areregistered.)
Once connected, you can send commands as follows:
# Send text messagesws$send("hello")# Send binary messagesws$send(charToRaw("hello"))# Finishws$close()Note that if you want tosend() a message as soon as itconnects, without having to wait at the console, you can put thews$send() inside of thews$onOpen callback, asin:
ws<- WebSocket$new("wss://echo.websocket.org/")ws$onMessage(function(event) {cat("Client got msg: ", event$data,"\n")})ws$onOpen(function(event) { ws$send("hello")})The websocket (client) package can be used with a WebSocket server,implemented as a httpuv web application, to act as a WebSocket proxy.This proxy can be modified do things like log the traffic in eachdirection, or modify messages sent in either direction.
The proxy will listen to port 5002 on the local machine, and connectto the remote machine at wss://echo.websocket.org:80. In this example,after starting the proxy, we’ll connect to it with a WebSocket client ina separate R process, then send a message from that process. Here’s whatwill happen in the proxy:
"hello"."hello" from the client, convertit to"HELLO", then send it to the remote echo server."HELLO" and send itback."HELLO" from the server, convertit to"HELLO, world", then send it to the client."HELLO, world".To run this proxy, run the code below in an R session:
library(curl)library(httpuv)library(websocket)# URL of the remote websocket servertarget_host<-"echo.websocket.org:80"# Should be "ws" or "wss"target_protocol<-"ws"# Port this computer will listen onlisten_port<-5002# ==============================================================================# Functions for translating header strings between HTTP request and Rook formats# ==============================================================================req_rook_to_curl<-function(req, host) {# Rename headers. Example: HTTP_CACHE_CONTROL => Cache-Control r<-as.list(req)# Uncomment to print out request headers# cat("== Original ==\n")# cat(capture.output(print(str(r))), sep = "\n") r<- r[grepl("^HTTP_",names(r))] nms<-names(r) nms<-sub("^HTTP_","", nms) nms<-tolower(nms) nms<-gsub("_","-", nms,fixed =TRUE) nms<-gsub("\\b([a-z])","\\U\\1", nms,perl =TRUE)names(r)<- nms# Overwrite host field r$Host<- host# Uncomment to print out modified request headers# cat("== Modified ==\n")# cat(capture.output(print(str(r))), sep = "\n") r}resp_httr_to_rook<-function(resp) { status<-as.integer(sub("^HTTP\\S+ (\\d+).*","\\1", curl::parse_headers(resp$headers)[1]))list(status = status,headers =parse_headers_list(resp$headers),body = resp$content )}# ==============================================================================# Websocket proxy app# ==============================================================================# These functions are called from the server app; defined here so that they# can be modified while the application is running.onHeaders<-function(req) {# Print out the headers received from server# str(as.list(req$HEADERS))NULL}call<-function(req) { req_curl<-req_rook_to_curl(req, target_host) h<-new_handle()do.call(handle_setheaders,c(h, req_curl)) resp_curl<-curl_fetch_memory(paste0("http://", target_host, req$PATH_INFO),handle = h)resp_httr_to_rook(resp_curl)}onWSOpen<-function(clientWS) {# The httpuv package contains a WebSocket server class and the websocket# package contains a WebSocket client class. It may be a bit confusing, but# both of these classes are named "WebSocket", and they have slightly# different interfaces. serverWS<- websocket::WebSocket$new(paste0(target_protocol,"://", target_host)) msg_from_client_buffer<-list()# Flush the queued messages from the client flush_msg_from_client_buffer<-function() {for (msgin msg_from_client_buffer) { serverWS$send(msg) } msg_from_client_buffer<<-list() } clientWS$onMessage(function (isBinary, msgFromClient) {cat("Got message from client: ", msgFromClient,"\n")#NOTE: This is where we modify the messages going from the client to the# server. This simply converts to upper case. You can modify to suit your# needs. msgFromClient<-toupper(msgFromClient)cat("Converting toupper() and then sending to server: ", msgFromClient,"\n")if (serverWS$readyState()==0) { msg_from_client_buffer[length(msg_from_client_buffer)+1]<<- msgFromClient }else { serverWS$send(msgFromClient) } }) serverWS$onOpen(function(event) { serverWS$onMessage(function(msgFromServer) {cat("Got message from server: ", msgFromServer$data,"\n")#NOTE: This is where we could modify the messages going from the server# to the client. You can modify to suit your needs. msg<-paste0(msgFromServer$data,", world")cat('Appending ", world" and then sending to client: ', msg,"\n") clientWS$send(msg) })flush_msg_from_client_buffer() })}# Start the websocket proxy apps<-startServer("0.0.0.0", listen_port,list(onHeaders =function(req) {onHeaders(req) },call =function(req) {call(req) },onWSOpen =function(clientWS) {onWSOpen(clientWS) } ))# Run this to stop the server:# s$stop()# If you want to run this code with `Rscript -e "source('server.R')"`, also# uncomment the following so that it doesn't immediately exit.# httpuv::service(Inf)In a separate R session, you can connect to this proxy and send amessage.
# Connect to proxyws<- websocket::WebSocket$new("ws://localhost:5002")ws$onMessage(function(event) {cat(paste0('Received message from proxy: "', event$data,'"\n'))})# Send message to proxyws$send("hello")#> Received message from proxy: "HELLO, world"In the R process running the proxy, you will see:
Got message from client: helloConverting toupper() and then sending to server: HELLOGot message from server: HELLOAppending ", world" and then sending to client: HELLO, worldThis is a simple WebSocket echo server implemented with httpuv. Youcan run it and interact with using the WebSocket client code below.
library(httpuv)cat("Starting server on port 8080...\n")s<-startServer("0.0.0.0",8080,list(onHeaders =function(req) {# Print connection headerscat(capture.output(str(as.list(req))),sep ="\n") },onWSOpen =function(ws) {cat("Connection opened.\n") ws$onMessage(function(binary, message) {cat("Server received message:", message,"\n") ws$send(message) }) ws$onClose(function() {cat("Connection closed.\n") }) } ))This code will connect to the echo server and send a message:
library(websocket)ws<- WebSocket$new("ws://127.0.0.1:8080/",headers =list(Cookie ="Xyz"),accessLogChannels ="all"# enable all websocketpp logging)ws$onOpen(function(event) {cat("Connection opened\n")})ws$onMessage(function(event) {cat("Client got msg: ", event$data,"\n")})ws$onClose(function(event) {cat("Client disconnected with code ", event$code," and reason ", event$reason,"\n",sep ="")})ws$onError(function(event) {cat("Client failed to connect: ", event$message,"\n")})ws$send("hello")ws$send(charToRaw("hello"))ws$close()If you want it to send the message as soon as it connects (withouthaving to wait for a moment at the console), you can tell it to do thatin theonOpen callback:
ws$onOpen(function(event) {cat("Connection opened\n") ws$send("hello")})