TCPSocket, send always transmit an even length message

[Borna N.]

Hello all

Just a quick and obscure bug report

Console 1:

$ irb

require 'socket' => true
s = TCPSocket.open('localhost', 2000)

s.send('ab', 2) => 2
s.send('cde', 3)

=> 3

Console 2:
$ nc -l 2000
abcd

Write seems to work OK and puts too, but I could swear I had the same
issue with puts on another Ubuntu box with same specs and ruby 1.8.7.
I'm using Ubuntu 10.10, 2.6.35-27 kernel and ruby 1.9.2-p180 and ruby
1.8.7.

 

[Borna N.]

...this is not a flushing issue btw, adding flush at the end yields the
same result (letter e never shows up).

 

[Brian Candler]

I think you're using the wrong method.

'send' is a inherited method of BasicSocket, and calls 'sendto' in the
underlying O/S. And the second argument is actually flags, not length.

/*
* call-seq:
* basicsocket.send(mesg, flags [, dest_sockaddr]) => numbytes_sent
*
* send _mesg_ via _basicsocket_.
*
* _mesg_ should be a string.
*
* _flags_ should be a bitwise OR of Socket::MSG_* constants.
*
* _dest_sockaddr_ should be a packed sockaddr string or an addrinfo.
*
* TCPSocket.open("localhost", 80) {|s|
* s.send "GET / HTTP/1.0\r\n\r\n", 0
* p s.read
* }
*/

Try setting flags to zero instead and it'll probably work:

require 'socket' => true
rx = TCPServer.new('127.0.0.1',2000)

tx = TCPSocket.new('127.0.0.1',2000)

s = rx.accept

tx.send('ab', 0) => 2
tx.send('cde', 0) => 3
s.readpartial(1024) => "abcde"
RUBY_DESCRIPTION => "ruby 1.8.7 (2010-06-23 patchlevel 299) [x86_64-linux]"

But really you should just be using 'write' not 'send', unless you're
trying to do something funky like sending out-of-band data (MSG_OOB)