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Ruby中socket编程时出现recv for buffered IO (IOError) 错误的解决方法

王朝other·作者佚名  2006-06-27
窄屏简体版  字體: |||超大  

用Socket作异步编程时,检验对端是否已经关闭不能用Socket#eof?,因为这样会造成Ruby将此Socket的IO对象转换成Buffered IO,从而导致recv,recvfrom系列函数读取失败,出现“recv for buffered IO (IOError)”错误。在Buffered IO上只能调用可能会阻塞的read,readline,gets系列函数,严重影响了异步通信服务器的性能。

我也被这个问题困扰了好几天,直到在ruby新闻组中看到一篇很好的解决方案,用异常代替eof?检查,我已经在ruby1.8.2 windows one-click版本上测试通过,特此引用。原帖可在http://groups.google.com/group/comp.lang.ruby/msg/3fabd75cf9a38c1c上找到。

顺便补一句,几乎所有的教学资料上都使用Socket#eof?这个方法,而很少谈到这个错误,真是很奇怪。

Socket programming: recv(bytes) throwing a buffered IO error

Frank Swarbrick <info...@earthlink.net>

Eric Haase wrote:

> Hello everyone,

> 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

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

 
 
 
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