Ruby socket does not get reply

ruby-talk
1

Hi all,

I use a TCP connection and send some data like this:

  begin
    session = "mysession"
    socket = TCPSocket.new(tcpaddress, port)
    socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
    puts "sending to socket HELO " + session
    socket.write ('HELO ' + session)
    puts socket.read
    socket.close
  rescue Exception => myException
    puts "Exception rescued : #{myException}"
  end

The socket never gets a reply, however telnet does:

$ telnet some_ip port
Trying some_ip...
Connected to some_ip
Escape character is '^]'.
HELO mysession
OK

As you can see the remote server replies "OK" as expected. What's wrong?

Thanks in advanced!

PS: I have used puts and send methods also

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2

Robert Garrido wrote in post #998563:

As you can see the remote server replies "OK" as expected. What's wrong?

If the server is expecting 'line oriented input', then the server will
continue trying to read from the socket until it encounters a newline,
i.e. you need to end the data you send with a newline.

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3

    puts socket.read

This call (read) blocks until the other end of the connection closes it.
-r

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4

Roger Pack wrote in post #998583:

    puts socket.read

This call (read) blocks until the other end of the connection closes it.
-r

Good one. From IO#read docs:

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===
ios.read([length [, buffer]]) → string, buffer, or nil

If length is omitted or is nil, it reads until EOF...

When the server closes the socket, ruby sends an EOF signal to the other
side.

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5

This is the fix:

socket.write("HELO " + session + "\r\n")

Thanks :smiley:

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6

Robert Garrido wrote in post #998661:

This is the fix:

socket.write("HELO " + session + "\r\n")

Thanks :smiley:

Just be aware that ruby is going to convert a "\n" to "\r\n" on windows,
so on windows you will actually be wrting:

"\r\n"
= "\r" + "\n"
= "\r" + "\r\n"
= "\r\r\n"

That may or may not make a difference to a particular program.

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7

7stud -- wrote in post #998709:

That may or may not make a difference to a particular program.

One way to avoid the newline conversion is to use the actualy ascii code
for a newline instead of "\n":

"\r\n" in octal:

"\015\012"

"\r\n" in hex:

"x0D\x0A"

To avoid the ugliness of those escape sequences, perl has the constant
CRLF, which can be used in strings, when correct reading of the data
requires that line endings be marked by exactly one "\r" and one "\n".
However, I don't think ruby copied that feature from perl.

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8

Just be aware that ruby is going to convert a "\n" to "\r\n" on windows,
so on windows you will actually be wrting:

"\r\n"
= "\r" + "\n"
= "\r" + "\r\n"
= "\r\r\n"

That may or may not make a difference to a particular program.

I don't have a Windows system to test on but I'm pretty sure that sockets are always automatically opened in binary mode. On my Mac OS system:

socket = TCPSocket.new("www.google.com", 80)

=> #<TCPSocket:fd 4>
irb > socket.binmode?
=> true

The HTTP protocol requires "\r\n" line endings though so they have to be written explicitly on the binary socket as described in the earlier messages.

Gary Wright

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On May 14, 2011, at 1:16 PM, 7stud -- wrote: