Socket programming: recv(bytes) throwing a buffered IO error
Eric Haase
I just started learning Ruby and I decided to mess around with
socket programming. However, I've encountered a problem and was
wondering if someone could help me out. I wrote a server and a client
program and the server is behaving strange when I invoke the
recv(bytes) method in the TCPSocket class. Here is my server code with
the error I'm receiving:
require 'socket'
abort "usage: #{__FILE__} [port]" if ARGV.size > 1
port = (ARGV[0] || 3434).to_i
server = TCPServer.new(port)
sockets = [server]
puts "listening on port ##{port}"
loop do
socketsReady = select(sockets)
next if socketsReady == nil
socketsReady[0].each do |socket|
if socket == server
client = socket.accept
sockets.push(client)
puts "established connection
(#{client.addr[-1]}:#{client.addr[1]})"
else
if socket.eof?
address = socket.addr
sockets.delete(socket)
socket.close
puts "closed connection (#{address[-1]}:#{address[1]})"
else
string = socket.recv(1024)
puts "received \"#{string}\"
(#{socket.addr[-1]}:#{socket.addr[1]})"
socket.puts(" server received your \"#{string}\"")
end
end
end
end
./server_bad.rb:27:in `recv': recv for buffered IO (IOError)
from ./server_bad.rb:27
from ./server_bad.rb:15
from ./server_bad.rb:12
The client code is as follows:
require 'socket'
abort "usage: #{__FILE__} [address] [port]" if ARGV.size != 2
socket = TCPSocket.new(ARGV[0],ARGV[1])
socket.send('hello',0)
socket.close
I can't seem to decipher the error code but one thing I did notice is
that when I use the same client code with the following server code
everything turns out fine:
require 'socket'
abort "usage: #{__FILE__} [port]" if ARGV.size != 1
server = TCPServer.new(ARGV[0].to_i)
socket = server.accept
puts "\"#{socket.recv(1024)}\""
socket.close
Anyone have any idea whats going on? The only relevant code that could
possibly cause the difference between the working server and the server
producing the error is the select method but I don't know why. If
someone can explain whats going on and how I could go about solving it
I would really appreciate it. Also, I've gotten them both to work with
'puts' and 'gets' but I don't want my system to retrieve bytes until a
newline. Any input would be appreciated. Thanks in advance for your
time!
Frank Swarbrick
I'm not sure about all of the issues, but I think it may have to do with
you attempting to test socket.eof? prior to reading from socket. I
don't think it can know about it's eof status until it does the read.
I'm just a Ruby beginner, but I know socket programming pretty well.
Try replacing the inside of the socketsReady[0].each loop as follows:
if socket == server
client = socket.accept
sockets.push(client)
puts "established connection" +
"(#{client.addr[-1]}:#{client.addr[1]})"
else
begin
string = socket.recv(1024)
puts "received \"#{string}\""+
"(#{socket.addr[-1]}:#{socket.addr[1]})"
socket.write(" server received your \"#{string}\"")
rescue
address = socket.addr
sockets.delete(socket)
socket.close
puts "closed connection (#{address[-1]}:#{address[1]})"
end
end
Seems to work. Now you need to figure out how to abort from the loop,
such as when the user enters a key (on the server process). I can't
figure it out...
Frank