解決bind錯誤 bind: Address already in use

關於bind錯誤的處理：
bind: Address already in use

緣由： 操做系統沒有當即釋放端口

解決一： 等待一段時間運行網絡程序便可

解決二：經過setsockopt進行設置，關鍵代碼以下。

1         // 解決在close以後會有一個WAIT_TIME，致使bind失敗的問題
2     int val = 1;
3     int ret = setsockopt(sfd,SOL_SOCKET,SO_REUSEADDR,(void *)&val,sizeof(int));
4     if(ret == -1)
5     {
6         printf("setsockopt");
7         exit(1);
8     }     

舉例：以多進程併發服務器爲例

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <string.h>
 4 
 5 #include <sys/types.h>  
 6 #include <sys/socket.h>
 7 #include <netinet/in.h>
 8 #include <arpa/inet.h>
 9 #include <signal.h>
10 
11 #define PORT 7788
12 
13 int init_tcp()
14 {
15     // 1.建立套接字 - 設置協議
16     int sfd = socket(AF_INET,SOCK_STREAM,0);
17     if( -1 == sfd )
18     {
19         perror("socket");
20         exit(-1);
21     }
22     //2. 解決在close以後會有一個WAIT_TIME，致使bind失敗的問題
23     int val = 1;
24     int ret = setsockopt(sfd,SOL_SOCKET,SO_REUSEADDR,(void *)&val,sizeof(int));
25     if(ret == -1)
26     {
27         printf("setsockopt");
28         exit(1);
29     }
30     //3. 綁定IP和PORT
31     struct sockaddr_in saddr;
32     saddr.sin_family = AF_INET;
33     saddr.sin_addr.s_addr = INADDR_ANY;
34     saddr.sin_port = htons(PORT);
35     ret = bind(sfd,(struct sockaddr *)&saddr,sizeof(saddr));
36     if(ret == -1)
37     {
38         printf("bind");
39         exit(1);
40     }
41     //4. 監聽
42     ret = listen(sfd,5);
43     if(ret == -1)
44     {
45         printf("listen");
46         exit(1);
47     }
48     printf("Server is ready ... \n");
49     
50     return sfd;
51 }
52 
53 void deal_communication(int cfd)
54 {
55     char buf[64] = {'\0'};
56     while(1)
57     {
58         memset(buf,'\0',sizeof(buf));
59         recv(cfd,buf,sizeof(buf),0);
60         printf("client say:%s\n",buf);
61         send(cfd,buf,strlen(buf),0);
62         if(strncmp(buf,"quit",4) == 0)
63         break;                
64     }
65 
66     return ;
67 }
68 
69 
70 int main()
71 {
72     //1. 初始化(建立套接字socket/地址複用+bind/listen)
73     int sfd = init_tcp();
74     //2. 併發處理客戶端（accept / fork） 2-2通訊
75     while(1)
76     {
77         int cfd = accept(sfd,NULL,NULL);
78         if(cfd == -1)
79         {
80             perror("accept");
81             exit(1);
82         }
83         
84         // fork - create a child process
85         if(fork() == 0)
86         {
87             deal_communication(cfd);
88             close(cfd);
89             exit(0);
90         }
91         close(cfd);
92         signal(SIGCHLD,SIG_DFL);
93     }
94     close(sfd);
95     return 0;
96 }