C/C++网络编程中的TCP保活

 1 #include <stdlib.h>   
 2 #include <fcntl.h>    
 3 #include <errno.h>    
 4 #include <sys/socket.h>    
 5 #include <netinet/tcp.h>    
 6 #include <netinet/in.h>    
 7 #include <netdb.h>    
 8 #include <arpa/inet.h>    
 9     
10 int    
11 socket_set_keepalive (int fd)    
12 {    
13   int ret, error, flag, alive, idle, cnt, intv;    
14     
15   /* Set: use keepalive on fd */    
16   alive = 1;    
17   if (setsockopt    
18       (fd, SOL_SOCKET, SO_KEEPALIVE, &alive,    
19        sizeof alive) != 0)    
20     {    
21       log_warn ("Set keepalive error: %s.\n", strerror (errno));    
22       return -1;    
23     }    
24     
25   /* １０秒钟无数据，触发保活机制，发送保活包 */    
26   idle = 10;    
27   if (setsockopt (fd, SOL_TCP, TCP_KEEPIDLE, &idle, sizeof idle) != 0)    
28     {    
29       log_warn ("Set keepalive idle error: %s.\n", strerror (errno));    
30       return -1;    
31     }    
32     
33   /* 如果没有收到回应，则５秒钟后重发保活包 */    
34   intv = 5;    
35   if (setsockopt (fd, SOL_TCP, TCP_KEEPINTVL, &intv, sizeof intv) != 0)    
36     {    
37       log_warn ("Set keepalive intv error: %s.\n", strerror (errno));    
38       return -1;    
39     }    
40     
41   /* 连续３次没收到保活包，视为连接失效 */    
42   cnt = 3;    
43   if (setsockopt (fd, SOL_TCP, TCP_KEEPCNT, &cnt, sizeof cnt) != 0)    
44     {    
45       log_warn ("Set keepalive cnt error: %s.\n", strerror (errno));    
46       return -1;    
47     }    
48     
49   return 0;    
50 }