[R-pkg-devel] socketConnection, delay when reading from

[Ben Engbers]

Op 07-12-2021 om 23:49 schreef Ben Engbers:

After a long nightly session, I ended up with inserting a wait between 
sending the authentication nonce and reading the status byte.

writeBin(auth, private$conn)
Sys.sleep(.1)
Accepted <- readBin(conn, what = "raw", n = 1)

The new code, which now uses a non-blocking socket, takes less than 4 
seconds to execute the 53 tests. Compared to the 120 seconds when using 
a blocking socket, this was worth the effort.

Ben


> Hi Tomas,
> 
> I have implemented your suggestions as follows: (I'm not certain yet if 
> the first check in done - total_length == 0 is realy needed)
> 
> Creating the socket:
> 
> CreateSocket = function(host, port = 1984L, username, password) {
>    tryCatch(
>      {conn <- private$conn <- socketConnection(
>        host = "localhost", port,
>        open = "w+b", server = FALSE, blocking = FALSE, encoding = "UTF-8")
>      }, error = function(e) {
>        stop("Cannot open the connection")
>       }
>    )
> 
> #### Authenticating
> 
> response <- readBin_(conn) %>% rawToChar()
> ===> # browser()
> splitted <-strsplit(response, "\\:")
> ifelse(length(splitted[[1]]) > 1,
>    { realm <- splitted[[1]][1]
>      code  <- paste(username, realm, password, sep=":")
>      nonce <- splitted[[1]][2] },
>    { code  <- password
>      nonce <- splitted[[1]][1]}
>    )
> code <- md5(paste(md5(code), nonce, sep = "")) %>% charToRaw()
> # send username + code
> auth <- c(charToRaw(username), as.raw(0x00), code, as.raw(0x00))
> writeBin(auth, private$conn)
> Accepted <- readBin(conn, what = "raw", n = 1) == 0x00
> if (!Accepted) {
> close(private$conn)
> stop("Access denied")
> }

> The first time readBin is used is while authenticating a new session.
> This code fails ;-(
> 
> But when I insert a  call to browser() after the first authentication 
> line, I can execute all the following code without problems. This 
> results in a fully functional session. And all the other following calls 
> to readBin_ return the correct data.
> This means that 'done' and 'readBin' do exactly what they are intended 
> to do.
> 
> Question
> Why does creating and authenticating fail when a call to browser() is 
> missing? (Or why does authentication succeed after I have used the debugger?
> 
> Best,
> Ben