LwIP develops | socket | TCP | keepalive heartbeat mechanism

** Reference resources ：**https://blog.csdn.net/Chuangke_Andy/article/details/113116289

** significance ：** Improve each platform lwip TCP/UDP Programming compatibility , Portability

Environmental Science :
1.freertos
2. Turn on LWIP_SOCKET & LWIP_TCP_KEEPALIVE
3. Bgi, HC32F4A0( Compatible )

Programming

#include "lwip_keepalive.h"
#include "lwip/opt.h"
#include <lwip/sockets.h>
#include "lwip/sys.h"
#include "lwip/api.h"
#include "string.h"

//https://blog.csdn.net/Chuangke_Andy/article/details/121420376
#if (LWIP_SOCKET & LWIP_TCP_KEEPALIVE)

#define DEST_PORT (6134UL)// Destination address port number  
#define DEST_IP "192.168.2.195"/* Destination address IP, This is set as local */ 
#define MAX_DATA (1024UL)// The maximum amount of data received  

#define LWIP_KEEPALIVE_DEBUG_ENABLE 1
#if LWIP_KEEPALIVE_DEBUG_ENABLE
   #define LWIP_KEEPALIVE_DEBUG printf
#else
  #define LWIP_KEEPALIVE_DEBUG(...)
#endif
 
#define BUFF_SIZE (1024UL)
static char ReadBuff[BUFF_SIZE];
void lwip_keepalive_thread(void *arg)
{
    
	int sockfd, n, i, ret;
	struct sockaddr_in dest_addr;
	int so_keepalive_val = 1;   // Enable the heartbeat mechanism 
	int tcp_keepalive_idle = 3; // Send heartbeat idle cycle  S 
	int tcp_keepalive_intvl = 3;// Send heartbeat interval  S
	int tcp_keepalive_cnt = 3;	// Number of retransmissions 
	int tcp_nodelay = 1;		// Send to the merge package without delay 
	
again:
	
	// establish scoket
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	// Enable the heartbeat mechanism 
	setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &so_keepalive_val, sizeof(int));
	
	dest_addr.sin_family = AF_INET;
	dest_addr.sin_port = htons(DEST_PORT);
	dest_addr.sin_addr.s_addr = inet_addr(DEST_IP);

    inet_aton(DEST_IP,&dest_addr.sin_addr);/* Convert the dotted decimal system to 32 Bit integer type */
    if(connect(sockfd,(struct sockaddr*)&dest_addr,sizeof(struct sockaddr)) < 0)
	{
    
		// Connection method , Incoming handle , Destination address and size  
		//100ms Connect to the server once 
		LWIP_KEEPALIVE_DEBUG("connect error\r\n");
		close(sockfd);
		vTaskDelay(100);
		goto again;
	}
	
	// Configure heartbeat detection parameters   The default parameter takes a long time 
	setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPIDLE, &tcp_keepalive_idle, sizeof(int));	
	setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPINTVL, &tcp_keepalive_intvl, sizeof(int));	
	setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPCNT, &tcp_keepalive_cnt, sizeof(int));	
	setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, &tcp_nodelay, sizeof(int));
	
	LWIP_KEEPALIVE_DEBUG("server is connect ok\r\n");

	for(;;)
	{
    
		// Wait for the server to send data 
		n = read(sockfd, ReadBuff, BUFF_SIZE);
		if(n <= 0)
		{
    
			LWIP_KEEPALIVE_DEBUG("read socket error\r\n");			
			close(sockfd);
			goto again;	
		}
		// Write back to server 
		n = write(sockfd, ReadBuff, n);
		if(n <= 0)
		{
    
			close(sockfd);
			goto again;	
		}		
	}
}
#endif
void lwip_keepalive_init(void)
{
    
#if LWIP_SOCKET
  sys_thread_new("lwip_keepalive_thread", lwip_keepalive_thread, NULL, 512, 4);
#endif
}