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Below is a simple script to find out whether all files exists and are having size greater than zero or not. From here I know '-s' is used for the task.

My C++ client side socket code only collects the very first line of the output provided by an Arduino socket server (I guess I can call it that). Can you please tell me where I am going wrong with my C++ code and how to fix it? If the question is too verbose please jump to the C++ code at the bottom.

Hardware setup: Arduino Mega with an Ethernet card (shield) and an Intel NUC with Ubuntu 16.04. The two devices are connected using cable and an unmanaged switch.

Arduino Side: I started out with a web server example from the Arduino Ethernet library, and modified the code until I was able to collect the status of all I/O, process the I/O data, and make results available to a web client. Image below shows a snapshot of the HTML my Arduino dishes out.

The Arduino code that handles the socket server side of things is as follows (everything works, but thought to include to show everything):

I need to use NGINX as a WebSocket Proxy, and I've been able to run this tutorial without any problem. In this case, a simple WebSocket application is done using ws and Node.js. However, I need to substitute the code in javascript (server.js) with an application developed in C.

To do so, I've tried with the last example shown in this tutorial, which is very simple and easy to understand.

However, using the same port and configuration as in server.js, when running the compiled C code, it seems that the communication is not properly established. In this case, when I run wscat in the client's terminal, it seems it is waiting for something since the word 'connected' is never seen, but the communication is not finished either (this is why I say it seems it is waiting for something; in other cases, if I try with a different port, for instance, the communication is closed and it appears a sentence as 'error: unexpected server response').

On the other hand, on the server side, I can see there is a new connection. I suspect that the answer from the server is not arriving at the client, but I don't know why. Nginx is properly configured since the example done in javascript works properly, and I'm using the same ports in both javascript and C (in server.js I have: 'wss = new WebSocketServer({port: 8010});' and in server.c: 'server.sin_port = htons( 8010 );' from my point of view it should work...)

I've tried with other examples in C with a similar behavior. Does anyone know which may be the cause for this? Do you recommend other particular C codes for WebSocket servers?