svSocket (version 0.9-48)

evalServer: Evaluate R code in a server process

Description

This function is designed to connect two R processes together using the socket server. This function allows for piloting the server R process from a client R process, to evaluate R code in the server and return its results to the client.

Usage

evalServer(con, expr, send = NULL)

Arguments

con

A socket connection with the server (see examples)

expr

An R expression to evaluate in the server

send

Optional data to send to the server

Value

• The object returned by the last evaluation in the server.

See Also

sendSocketClients

Examples

# Start an R process and make it a server
require(svSocket)
startSocketServer()

# Start a second R process and run this code in it (the R client):
require(svSocket)

# Connect with the R socket server
con <- socketConnection(host = "localhost", port = 8888, blocking = FALSE)

L <- 10:20
L
evalServer(con, L)    # L is not an the server, hence the error
evalServer(con, L, L) # Send it to the server
evalServer(con,L)     # Now it is there
evalServer(con, L, L + 2)
L
evalServer(con, L)

# More examples
evalServer(con,"x = 42")       # set x
evalServer(con,"y = 10")
evalServer(con, x + y)         # don't need quotes
evalServer(con, "x + y")       # but you can put quotes if you like
evalServer(con, x)             # same as get x
evalServer(con, "x + Y")       # returns server side error to the client
evalServer(con, x)             # keeps working after an error
evalServer(con, "x = 'a'")     # embedded quotes are ok

# Examples of sending data
evalServer(con, X, -42)        # alternative way to assign to X
evalServer(con, Y, 1:10)
evalServer(con, X + Y)
X  # Generates an error, X is not here in the client, only on the server
evalServer(con, X)
evalServer(con, "Z <- X + 3")  # send an assignment to execute remotely
evalServer(con, X + Z)
evalServer(con, "Z <- X + 1:1000; NULL")   # same but prevents Y being returned
evalServer(con, length(Z))
Z <- evalServer(con, Z)           # bring it back to client
Z

# Close connection with the R socket server
close(con)

# Now, switch back to the R server process and check
# that the created variables are there
L
x
y
X
Y
Z