Coding a server

Ruby
1

Hey,

I’m porting some old c++ code for a server to ruby, and I can’t figure
out what’s the correct way of doing the network packet parsing

I’m using eventmachine for the networking code but when a packet is
received it must be parsed and depending on the header the packet will
have one format or another, and each of these would have an associated
reply format, I’m not quite sure on how to code this while keeping it
clean

Any ideas on how you would do this?
also, in cpp I’m using structs for the packet formats, but I have no
idea on how to do that in ruby

2

On Mon, Jan 05, 2009 at 04:24:02PM +0900, Vernier – wrote:

Any ideas on how you would do this?
also, in cpp I’m using structs for the packet formats, but I have no
idea on how to do that in ruby

Take a look at packetfu Google Code Archive - Long-term storage for Google Code Project Hosting.

enjoy,

-jeremy

3

Jeremy H. wrote:

On Mon, Jan 05, 2009 at 04:24:02PM +0900, Vernier – wrote:

Any ideas on how you would do this?
also, in cpp I’m using structs for the packet formats, but I have no
idea on how to do that in ruby

Take a look at packetfu Google Code Archive - Long-term storage for Google Code Project Hosting.

enjoy,

-jeremy

the bindata dependency for packetfu is exactly what I was looking for
for the structs, thanks a lot

4

Vernier – wrote:

the bindata dependency for packetfu is exactly what I was looking for
for the structs, thanks a lot

Another option:

http://redshift.sourceforge.net/bit-struct/

I don’t know bindata, but from a quick glance at the docs I see that it
does handle related fields, like length fields that specify the length
of another field. BitStruct does not do that.

Another difference is that BitStruct is a subclass of string, so it is
very efficient to send a bitstruct to a socket or file or perform other
string operations.

5

Vernier – wrote:

very efficient to send a bitstruct to a socket or file or perform other
modifications
Exactly. If you have big packets, and only need to access a few fields
(esp. fixed length), bit-struct is especially efficient. But if you want
to use accessors a lot, then other libs might be better. With
bit-struct, each field access may require pack/unpack, bit
masking/shifting, etc.

6

Joel VanderWerf wrote:

Another option:

BitStruct

I don’t know bindata, but from a quick glance at the docs I see that it
does handle related fields, like length fields that specify the length
of another field. BitStruct does not do that.

Another difference is that BitStruct is a subclass of string, so it is
very efficient to send a bitstruct to a socket or file or perform other
string operations.

amazing performance, for creating 10k instances of the same simple
struct (ruby 1.9 rc1):

         user     system      total        real

bindata 3.681000 0.000000 3.681000 ( 3.827000)
bit-struct 0.063000 0.000000 0.063000 ( 0.057000)

so bit-struct is actually a good choice for networking without any
modifications