Not allowed to re-bind socket to same port

[mpulis]

Hi,

I have an application where, upon an external event, a socket is opened to a remote server using TCP and a string is sent over it. A new socket is created each time, then closed and shutdown after the data is sent.

Now I've been informed by a client of ours that they wish the source port to remain constant. In order to implement a small change to the code, I've tried using the SO_REUSEPORT and SO_REUSEADDR options in order to be able to re-bind a socket to the same source port as previous sockets. The first socket works fine, but subsequent connections do not. What could be the issue here?

Code: Select all

	struct sockaddr_in destAddr;
	destAddr.sin_addr.s_addr = inet_addr(remote_ip);
	destAddr.sin_family = AF_INET;
	destAddr.sin_port = htons(remote_port);
	addr_family = AF_INET;
	ip_protocol = IPPROTO_IP;
	inet_ntoa_r(destAddr.sin_addr, addr_str, sizeof(addr_str) - 1);

	int sock =  socket(addr_family, SOCK_STREAM, ip_protocol);
	if (sock < 0) 
	{
		ESP_LOGE(TAG, "tcpClientTaskSocketAPI : Unable to create socket: errno %d", errno);
	}
	ESP_LOGI(TAG, "tcpClientTaskSocketAPI: Socket created");

	int option_value = 1;
	setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &option_value, sizeof(int));
	option_value = 1;
	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &option_value, sizeof(int));

	struct sockaddr_in sourceAddr;
	sourceAddr.sin_addr.s_addr = htonl(INADDR_ANY);
	sourceAddr.sin_family = AF_INET;
	sourceAddr.sin_port = htons(source_port);
	err_v = bind(sock, (struct sockaddr *)&sourceAddr, sizeof(sourceAddr));
	ESP_LOGW(TAG, "%d", err_v);

	int err = connect(sock, (struct sockaddr *)&destAddr, sizeof(destAddr));
	if (err != 0) 
	{
		ESP_LOGE(TAG, "tcpClientTaskSocketAPI: Socket unable to connect: errno %d", errno);
	}
	ESP_LOGI(TAG, "tcpClientTaskSocketAPI: Successfully connected");

	if(sock > 0)
	{
		send(sock, data, strlen(data), 0);
		ESP_LOGE(TAG, "tcpClientTaskSocketAPI: Shutting down socket and restarting...");

		shutdown(sock, 0);
		close(sock);
	}
    vTaskDelete(NULL);