Downloading data via ftp to use in shinyapp causes readRDS unknown input format error

Question

I am having trouble downloading data from an external ftp-source for use in a shinyapp. http://Shinyapps.io does not allow for writing to a file on the server, so we must avoid that and try saving externally with ftp and then later read it directly into memory from there.

See Wes Sauder at https://stackoverflow.com/a/32631356/3493503 for where I got started.

library(RCurl)
a <- "test"
saveRDS(a, file="data.Rdata")

data_path <- my_data_path
url <- my_ftp_url
ftpUpload(data_path, to=url, connecttimeout=120) #upload

bin = getBinaryURL(url, verbose = TRUE,
               ftp.use.epsv = TRUE)
readRDS(rawConnection(bin))

Uploading works fine, I can download the file with Filezilla afterwards and read it with readRDS. However, trying to download it in R with the above code does not work:

 > library(RCurl)
    > a <- "test"
    > saveRDS(a, file="data.Rdata")
    > data_path <- "**************"
    > url <-"ftp://******************/results.RData"
    > ftpUpload(data_path, to=url, connecttimeout=120) #upload
    OK 
    0 
    > bin = getBinaryURL(url, verbose = TRUE,
    + ftp.use.epsv = TRUE)
    *   Trying ***.***.***.***...
    * Connected to ******************** port 21 (#0)
    < 220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
    < 220-You are user number 9 of 50 allowed.
    < 220-Local time is now 10:43. Server port: 21.
    < 220-This is a private system - No anonymous login
    < 220-IPv6 connections are also welcome on this server.
    < 220 You will be disconnected after 15 minutes of inactivity.
    > USER ********
    < 331 User ******** OK. Password required
    > PASS ********
    < 230 OK. Current restricted directory is /
    > PWD
    < 257 "/" is your current location
    * Entry path is '/'
    > EPSV
    * Connect data stream passively
    * ftp_perform ends with SECONDARY: 0
    < 229 Extended Passive mode OK (|||31331|)
    *   Trying ********...
    * Connecting to ******** port 31331
    * Connected to ******** port 21 (#0)
    > TYPE I
    < 200 TYPE is now 8-bit binary
    > SIZE results.RData
    < 213 50
    > RETR results.RData
    < 150 Accepted data connection
    * Maxdownload = -1
    * Getting file with size: 50
    * Remembering we are in dir ""
    < 226-File successfully transferred
    < 226 0.000 seconds (measured here), 0.66 Mbytes per second
    * Connection #0 to host ******** left intact
    > readRDS(rawConnection(bin))
    Error in readRDS(rawConnection(bin)) : unknown input format

For the matter of completeness, I also tried

load(rawConnection(bin))
Error in load(rawConnection(bin)) : 
the input does not start with a magic number compatible with loading from a     connection

source(rawConnection(bin))
Error in source(rawConnection(bin)) : 
rawConnection(bin):1:1: unexpected input
1: 
   ^

Any solution/explanation/input is greatly appreciated.

I uploaded a file via Filezilla containing the RDS-object to http://webkartet.no/data.Rdata for you to try. It causes the same error.

Note: I tried to follow up in the comment-section of Wes Sauders answer, but was not able to do so, apparently due to a lack of SE-points. Tried to find solutions on SO without success.

Other information

platform x86_64-w64-mingw32
arch x86_64
os mingw32
system x86_64, mingw32
status
major 3
minor 3.1
year 2016
month 06
day 21
svn rev 70800
language R
version.string R version 3.3.1 (2016-06-21) nickname Bug in Your Hair

Using Windows 7