setsockopt函数--设置connect超时

r囧r小猫 2022-08-12 04:29 3阅读 0赞

http://blog.csdn.net/eroswang/article/details/4819444

原来我们实现connect()超时基本上都使用unix网络编程一书的非阻塞方式（connect\_nonb），今天在网上看到一篇文章，觉得很有意思，**转载**如下：

读Linux内核源码的时候偶然发现其connect的超时参数竟然和用SO\_SNDTIMO操作的参数一致:  
File: net/ipv4/af\_inet.c

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   <td>&nbsp;&nbsp;&nbsp; 559&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; timeo = sock_sndtimeo(sk, flags &amp; O_NONBLOCK);<br> &nbsp;&nbsp;&nbsp; 560<br> &nbsp;&nbsp;&nbsp; 561&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if ((1 &lt;&lt; sk-&gt;sk_state) &amp; (TCPF_SYN_SENT | TCPF_SYN_RECV)) { <br> &nbsp;&nbsp;&nbsp; 562&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* Error code is set above */<br> &nbsp;&nbsp;&nbsp; 563&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (!timeo || !inet_wait_for_connect(sk, timeo))<br> &nbsp;&nbsp;&nbsp; 564&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; goto out;<br> &nbsp;&nbsp;&nbsp; 565<br> &nbsp;&nbsp;&nbsp; 566&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; err = sock_intr_errno(timeo);<br> &nbsp;&nbsp;&nbsp; 567&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (signal_pending(current))<br> &nbsp;&nbsp;&nbsp; 568&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; goto out;<br> &nbsp;&nbsp;&nbsp; 569&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</td> 
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这意味着： **在Linux平台下，可以通过在connect之前设置SO\_SNDTIMO来达到控制连接超时的目的** 。简单的写了份测试代码:

**\[cpp\]**  [view plain][] [copy][view plain]

1.  \#include <stdlib.h>  
2.  \#include <stdio.h>  
3.  \#include <sys/types.h>  
4.  \#include <sys/socket.h>  
5.  \#include <netinet/in.h>  
6.  \#include <errno.h>  
7.  \#include <sys/socket.h>  
8.  \#include <netinet/in.h>  
9.  \#include <arpa/inet.h>  
10.   
11. **int** main(**int** argc, **char** \*argv\[\])  
12. \{  
13.         **int** fd;   
14.         **struct** sockaddr\_in addr;  
15.         **struct** timeval timeo = \{3, 0\};   
16.         socklen\_t len = **sizeof**(timeo);  
17.   
18.          fd = socket(AF\_INET, SOCK\_STREAM, 0);  
19.          **if** (argc == 4)  
20.                  timeo.tv\_sec = atoi(argv\[3\]);  
21.   
22.          setsockopt(fd, SOL\_SOCKET, SO\_SNDTIMEO, &timeo, len);  
23.          addr.sin\_family = AF\_INET;  
24.          addr.sin\_addr.s\_addr = inet\_addr(argv\[1\]);  
25.          addr.sin\_port = htons(atoi(argv\[2\]));  
26.   
27.         **if** (connect(fd, (**struct** sockaddr\*)&addr, **sizeof**(addr)) == -1) \{  
28.                 **if** (errno == EINPROGRESS) \{  
29.                         fprintf(stderr, "timeout/n");  
30.                         **return** -1;  
31.                 \}         
32.                 perror("connect");  
33.                 **return** 0;  
34.         \}         
35.         printf("connected/n");  
36.   
37.         **return** 0;  
38. \}

使用 ./cmd  ip地址  端口  超时秒数

(测试的ip和端口必须是不存在的，或者是ip的机器是死掉的，才会出现，否则机器存在而端口不存在会立即返回的)

[view plain]: http://blog.csdn.net/eroswang/article/details/4819444#