Make max message size configurable

[trestletech]

Closes #54

> ws <- WebSocket$new("ws://echo.websocket.org", maxMessageSize=3456)

Testing Notes

1. Try out really small maximums

This is intended to be run interactively! Running in a script will likely try to send before the connection is actually open.

ws2 <- websocket::WebSocket$new("ws://echo.websocket.org",
                                autoConnect = FALSE,
                                maxMessageSize=2)

ws2$onMessage(function(event) {
  message("Message received: ", event$data);
})
ws2$connect()
# MANUALLY WAIT
ws2$send(paste(rep("A", times=4), collapse=""))
ws2$close()

When you try to send/receive the message AAAA, you should get an error because the maximum size is 2 bytes.

2. Try out really large maximums

Start up a local websocket server so you can send really large messages successfully: https://github.com/rstudio/websocket/blob/master/tmp/websocketServer.R This will start a server on port 8080.

This is intended to be run interactively! Running in a script will likely try to send before the connection is actually open.

msgs <- NULL

ws2 <- websocket::WebSocket$new("ws://localhost:8080",
                                autoConnect = FALSE,
#                                maxMessageSize = 32 * 1024 * 1024) #32MB buffer (default)
#                                maxMessageSize = 50 * 1024 * 1024) #50MB buffer

ws2$onMessage(function(event) {
  msgs <<- c(msgs, event$data)
})
ws2$connect()
# MANUALLY WAIT
ws2$send(paste(rep("A", times=40000000), collapse="")) #Try sending a 40MB message
ws2$close()

When you try to send 40 million As, With the default maximum of 32MB, it should fail because it's too big. Once you up the max size to 50MB, you should then be able to send and receive such large messages. (This use case more accurately resembles the actual motivation for this work.)

[alandipert]

Code looks ✨ , thank you. Would you please also update testing notes in the PR and add a bullet to NEWS.md? I bumped the version on master to 1.1.0.9001 and made a heading under which you may add said bullet.

Thanks! 🙏