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Re: Help on sending a UDP Packet


From: Gary Highberger
Subject: Re: Help on sending a UDP Packet
Date: Tue, 12 Jan 2021 11:28:37 -0500

Hi David and everybody,

I just sent my first UDP packet with Smalltalk Sockets. It's likely just me
but there might be some instability in gst. Somehow my Datagram Socket got
wiped out. I'm going to run tests and publish my findings here.

Have GNU Smalltalk Sockets and the VM been proven in real world
applications?

Packet:
$ sudo tcpdump -i 1 -nn -n -A port 49152
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlp3s0, link-type EN10MB (Ethernet), capture size 262144 bytes
10:53:15.131345 IP 192.168.1.114.49153 > 192.168.1.249.49152: UDP, length 27
E..7..@.@..0...r.........#..  Hi sailor! New in town?

Smalltalk:
st> PackageLoader fileInPackage: 'Sockets'
"Global garbage collection... done"
Loading package Sockets
PackageLoader
st> DgS := Sockets.DatagramSocket remote: '192.168.1.249' port: 49152
local: '192.168.1.114' port: 49153
Sockets.DatagramSocket[192.168.1.114:49153]
st> DgD := Sockets.Datagram data: '  Hi sailor! New in town?  '
a Datagram
st> DgS nextPut: DgD
Sockets.DatagramSocket[192.168.1.114:49153]
Voila

Many thanks for the help everybody!

Gary

On Sun, Jan 10, 2021 at 1:49 PM Gary Highberger <gary.highberger@gmail.com>
wrote:

> Hello David and all,
>
> I have a few (noob) questions about the UDP example Smalltalk program.
> More questions likely to follow as I come up to speed. Your patience is
> much appreciated David and everybody.
>
> QUESTIONS:
> •  Is "_" the preferred assignment operator? I've been seeing ":=" too. I
> don't have a back arrow on my keyboard. I guess the PARC people used "_".
>
> •  Does statement 1)
> assign the destination IP address? Note that for my application, the
> source and destination addresses will be different.
>
> •  Does statement 3)
> populate the (UDP) datagram socket with the message, port, and address?
> Why a "#" symbol prefixing the message string, 'hello world'?
>
> •  Does statement 4)
> create a listening socket?
>
> •  Does statement 5)
> trigger the send?
>
> •  Does statement 6)
> block until the UDP response?
>
> +---------------------------------------------------------+
>
> UDP Smalltalk (example) program:
>
> 1) h _ Sockets.SocketAddress createLoopbackHost.
>
> 2) s _ Sockets.DatagramSocket new.
>
> 3) d _ Sockets.Datagram data:#'hello world' address:h port:13.
>
> 4) answer _ Sockets.Datagram new.
>
> 5) s nextPut:d.
>
> 6) s receive:answer.
>
> 7) (answer data) asString printNl.
>
> 8) s close.
>
> Gary Highberger
>
>
> On Sun, Jan 10, 2021, 8:48 AM Gary Highberger <gary.highberger@gmail.com>
> wrote:
>
>> Good morning David,
>>
>> I'm not familiar with 'daytime' but will come up to speed on it and get
>> it and your use cases running and report my findings for everybody to see.
>>
>> Hopefully netTest.c explains what I'm trying to do with Smalltalk. It's
>> very short and simple.
>>
>> https://www.dropbox.com/s/xc23wj6r5aqh153/netTest.c?dl=0
>>
>> I used my cell phone as the destination, my home WiFi as the network, and
>> tcpdump to see the packet.
>>
>> Thank you David for the Smalltalk code fragments and introducing me to
>> inetd and 'daytime'.
>>
>> Gary Highberger
>>
>>
>>


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