Does anyone have any advice on how to get started sending commands from FPC to use these ethernet relays:

https://www.amazon.com/gp/product/B076CNJNFH

Default IP :192.168.1.4 prot:30000 http://192.168.1.4/30000

HTTP Comment:
http://192.168.1.4/30000/00 : Relay-01 OFF
http://192.168.1.4/30000/01 : Relay-01 ON
http://192.168.1.4/30000/02 : Relay-02 OFF
http://192.168.1.4/30000/03 : Relay-02 ON
http://192.168.1.4/30000/04 : Relay-03 OFF
http://192.168.1.4/30000/05 : Relay-03 ON
...
http://192.168.1.4/30000/14 : Relay-8 OFF
http://192.168.1.4/30000/15 : Relay-8 ON
http://192.168.1.4/30000/41 : Enter
http://192.168.1.4/30000/40 : Exit
http://192.168.1.4/30000/42 : Next Page
http://192.168.1.4/30000/43 : Next Page

I don't really know what I even need to do to send commands like that over the network. Of course I can get it to work just typing the commands from a browser but that's not what I want, I want my FPC console program to send the appropriate commands whenever I want one of the relays to come on or go off.

Any suggestions on how this might be accomplished?

James

Hello James,

You'll find a source of happiness with unit fphttpclient . Particularily with the simplget function:

TFPHTTPCLIENT.SIMPLEGET('http://192.168.1.4/30000/00')

It is said that it works with https also, but under the Mageia7 distro, you probably encounter problems I haven't yet solved. But for http, that should be right.

Cheers, Ched

Le 24.05.20 à 18:46, James Richters a écrit :

Thanks!!
I'm happy with http, I should have mentioned I'm on Windows 10, any issues with that unit under windows?

James

I got this working, thanks for the advice Ched,

Here's my test program:
uses  fphttpclient;
Begin
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/01');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/03');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/05');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/07');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/43');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/09');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/11');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/13');
TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');
End.

I have to give it a command to go the next page for some reason or relays 5-8 won't work... so now I'm wondering if there is a way I can retrieve the data that is normally displayed in my browser to I can see what page number I'm on, I could also then check the status of the relays as well by analyzing what I read.

James

Simpleget is a function that returns the page:

S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');

S will contain the page of HTML.

If you need to send a command, you'll probably need to use SimplePost()

Michael.

Thanks!

Is there some convenient way to get the HTML into a Tstringlist?

James

James Richters wrote

Thanks! Is there some convenient way to get the HTML into a Tstringlist?

Yes. Simpleget is overloaded to accept a tstrings:

L:=TstringList.Create;
try
    TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/01',L);
finally
   L.Free;
end;

Michael.

Thank you Michael, I would have really overcomplicated that, glad I asked

James

I've been using simpleget to control ethernet relays like this:
S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');

But if the IP address does not exist on the network I get this error:

An unhandled exception occurred at $0000000100032A4A: ESocketError: Connection to 10.10.01.01:80 timed out.

And my program terminates. Is there some way I can capture this error with my program so I can just put up a message about the problem and keep running?

Is there a way to change the amount of time before the timeout?

James

Yes, catch the ESocketError in a try..except:

Try
   S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');
except
   On E: ESocketError do
     Writeln('Could not connect to server');
end;

Is there a way to change the amount of time before the timeout?

Yes, but then you need to create an instance, i.e. the Simple* commands won't do that for you:

Instead, it will look like this:

uses fphttpclient;
Var
   C : TFPHTTPClient;
begin
   C:=TFPHTTPClient.Create(Nil);
   try
      try
        C.ConnectTimeout:=10; // Or whatever you think is good
        C.Get('http://10.10.01.01/30000/15');
      except
        On E: ESocketError do
          Writeln('Could not connect to server');
      end;
   finally
     C.Free;
   end;
end;

Michael.

Thanks Michael, I'll give it a try

James

When I try to compile either of the examples below, I get Error: Identifier not found "ESocketError" Any ideas?

James

Yes, catch the ESocketError in a try..except:

Try
   S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');
except
   On E: ESocketError do
     Writeln('Could not connect to server'); end;

Is there a way to change the amount of time before the timeout?

Yes, but then you need to create an instance, i.e. the Simple* commands won't do that for you:

Instead, it will look like this:

uses fphttpclient;
Var
   C : TFPHTTPClient;
begin
   C:=TFPHTTPClient.Create(Nil);
   try
      try
        C.ConnectTimeout:=10; // Or whatever you think is good
        C.Get('http://10.10.01.01/30000/15');
      except
        On E: ESocketError do
          Writeln('Could not connect to server');
      end;
   finally
     C.Free;
   end;
end;

Michael.

Add the ssockets unit to your uses clause.

Michael

I added ssockets now I can compile it.

I have this working with the ssockets unit added:
Try
   S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');
 except
   On E: ESocketError do
     Writeln('Could not connect to server'); end;

But when I try the version with the timeout, I always get the error. What is the proper way to get the page into a variable with the timeout method? I tried S:= C.Get('http://10.10.01.01/30000/15'); But I'm not sure that's the right way to do it, but even without the S:= I always get the EsocketError

 uses fphttpclient,ssockets;
 Var
   C : TFPHTTPClient;
 begin
   C:=TFPHTTPClient.Create(Nil);
   try
      try
        C.ConnectTimeout:=10; // Or whatever you think is good
        C.Get('http://10.10.01.01/30000/15');
      except
        On E: ESocketError do
          Writeln('Could not connect to server');
      end;
   finally
     C.Free;
   end;
 end;

James

What timeout did you use ? 10 ms is probably too short.

Michael.

Yes 10 was too short, I made it larger and larger until it worked. 1000 was the lowest value that worked so I set it to 2000, that's still quite a bit faster than the default.

If I make a mistake in the link but the server IP address is correct, I get a valid connection but then it fails and terminates with: An unhandled exception occurred at $0000000100017675: EHTTPClient: Unexpected response status code: 401

If I use the wrong IP address, but that IP address has a different server running on it, but that page is not available, I get: An unhandled exception occurred at $0000000100017675: EHTTPClient: Unexpected response status code: 401

Is there a way to obtain these errors as well so it doesn't terminate my program?

James

Yes, catch the EHTTPClient exception just as you catch the ESocketError:

    try
      S:=TFPHTTPCLIENT.SIMPLEGET('http://10.10.01.01/30000/15');
    except
      On E: ESocketError do
       Writeln('Could not connect to server: ',E.Message);
      On EH : EHTTPClient do
       begin
       Writeln('Error getting the document : '+EH.Message);
       end;
    end;

If you created a TFPHTTPClient instance you can also examine the ResponseStatusCode property, it will contain the server response code.

Michael.

I put my project to control these ethernet relays on Git Hub at https://github.com/Zaaphod/Ethernet-HTTP-Relays/

I thought I would post it here so if someone comes across this while searching for information about them they will find it.

This is a library to control Ethernet Relays that use web browser commands similar to:

* http://192.168.1.4/30000/00 : Relay-01 OFF
* http://192.168.1.4/30000/01 : Relay-01 ON
* http://192.168.1.4/30000/02 : Relay-02 OFF
* http://192.168.1.4/30000/03 : Relay-02 ON
* http://192.168.1.4/30000/04 : Relay-03 OFF
* Http://192.168.1.4/30000/05 : Relay-03 ON
* ...
* http://192.168.1.4/30000/30 : Relay-16 OFF
* http://192.168.1.4/30000/31 : Relay-16 ON
* http://192.168.1.4/30000/41 : Enter
* http://192.168.1.4/30000/40 : Exit
* http://192.168.1.4/30000/42 : Next Page
* http://192.168.1.4/30000/43 : Next Page

These Relays are inexpensive and come either with a relay board or made to attach to common relay boards

It was tested with these boards:
--------------------------------
* 16 Relay: https://www.amazon.com/gp/product/B00NDS9LBK (Controller) With https://www.amazon.com/gp/product/B07Y2X4F77 (Relay Board)
* 8 Relay: https://www.amazon.com/gp/product/B076CNJNFH (comes with both the controller and the relay board)

It allows you to turn any relay on or off programmatically without using a web browser It also deciphers the pages provided by the board's web server to all you to programmatically get the status of each relay It can control multiple relay boards at the same time, they are referenced by their IP Address

James