[Solved] Recipes for being a TCP server ...

[kolban]

I am testing out logic on being a socket server. In my simple case, my goal was to start listening on an incoming socket port and merely log when a client connects. I created the following logic fragment using the sockets API which compiles cleanly.

Code: Select all

static void initSockets() {
	int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	printf("New sock = %d\n", sock);
	
	struct sockaddr_in serverAddress;
	serverAddress.sin_family = AF_INET;
	serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);
	serverAddress.sin_port = htons(80);
	int rc = bind(sock, (struct sockaddr *)&serverAddress, sizeof(serverAddress));
	checkSocketRC(rc, "bind");
	printf("bind completed!\n");
	
	rc = listen(sock, 10);
	checkSocketRC(rc, "listen");
	printf("listen completed!\n");
	
	struct sockaddr_in clientAddress;
	socklen_t clientAddressLength = sizeof(clientAddress);
	int clientSock = accept(sock, (struct sockaddr *)&clientAddress, &clientAddressLength);
	checkSocketRC(clientSock, "accept");
	printf("Accepted a client connection\n");
}

My questions relate to the correct architecture and flow constraints. For example, in this simple story, the accept() call is a blocking call. My understanding is that the ESP32 now runs two cores ... one for the network/wifi/others and the other core for user applications. Does this mean that I can now block in my app code with impunity?

Given that control is passed to me in app_main() ... can I block in app_main() or should I spawn a task at the FreeRTOS level and then block in that task?

When I run my app, it "seems" to work to a point. I see the messages. From a client machine, I can even form a connection to port 80 on the ESP32 and see the message that we accepted a client connection. Unfortunately, we then abend and I'm not yet anywhere near convinced what I attempted was valid ... hence the questions.

... a few days later ...
I found that my abend at the end of the function was caused by not calling vTaskDelete() which appears to be mandatory before ending a task. This was not related to any sockets issues. Further testing seems to show the sockets APIs functioning great and allow local task blocking without breaking the overall architecture.

[rcosta]

Hello Dear,

I would like to implement in the ESP32 a TCP Server. So, do you have the complete code?

Thanks in advance.

Sincerely,

Regivado Costa
--

[kolban]

When I learn something that is useful, I try and keep a snippet of it around ... my sockets snippets can be found here:

https://github.com/nkolban/esp32-snippe ... er/sockets