I O多路復用 select

int

select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);

timeout 為超時引數，呼叫 select 會一直阻塞直到有描述符的事件到達或者等待的時間超過 timeout。

成功呼叫返回結果大於 0，出錯返回結果為 -1，超時返回結果為 0。

select使用例項

服務端

1 #include 2 #include 3 #include in.h>

4 #include 5 #include 6 #include 7 #include 8 #include 9 #include 10 #include 
11 #include 12
#define default_port 6666
13int main( int argc, char **ar**)
22     printf("
socket ok \n");
23     my_addr.sin_family=af_inet;
24     my_addr.sin_port=htons(default_port);
25     my_addr.sin_addr.s_addr =inaddr_any;
26     bzero(&(my_addr.sin_zero), 0
);27
if (bind(serverfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr )) == -1
) 31     printf("
bind ok \n");
32if (listen(serverfd, lisnum) == -1
) 36     printf("
listen ok \n");
3738     fd_set client_fdset;    /*
監控檔案描述符集合
*/39
int maxsock;            /*
監控檔案描述符中最大的檔案號
*/40
struct timeval tv;        /*
超時返回時間
*/41
int client_sockfd[5];   /*
存放活動的sockfd
*/42     bzero((void*)client_sockfd,sizeof
(client_sockfd));
43int conn_amount = 0;    /*
用來記錄描述符數量
*/44     maxsock =serverfd;
45char buffer[1024
];46
int ret=0;47
while(1)61
}62/*printf("put sockfd in fdset!\n");
*/63
/*select函式
*/64     ret = select(maxsock+1, &client_fdset, null, null, &tv);
65if(ret < 0)69
else
if(ret == 0)73
/*輪詢各個檔案描述符
*/74
for(int i = 0; i < conn_amount; ++i)
85else88}
89}90/*
檢查是否有新的連線，如果收，接收連線，加入到client_sockfd中
*/91
if(fd_isset(serverfd, &client_fdset))
100/*
把連線加入到檔案描述符集合中
*/101
if(conn_amount < 5
)114     printf("
recv : %s\n
",buffer);
115if(sock_client >maxsock)
118else
122}
123}
124}
125for(int i = 0; i < 5; ++i)
129}
130close(serverfd);
131return
0;    
132 }

客戶端

1 #include 2 #include 3 #include 

4 #include 5 #include 6 #include 7 #include in.h>
8 #include 9 #include 10
#define default_port 6666
11int main( int argc, char *ar**)    
19     client.sin_family =af_inet;
20     client.sin_port =htons(default_port);
21     client.sin_addr.s_addr = inet_addr(ar**[1
]);22     connfd = socket(af_inet, sock_stream, 0
);23
if(connfd < 0)27
if(connect(connfd, (struct sockaddr*)&client, sizeof(client)) < 0)31
char buffer[1024
];32     bzero(buffer,sizeof
(buffer));
33     recv(connfd, buffer, 1024, 0
);34     printf("
recv : %s\n
", buffer);
35     bzero(buffer,sizeof
(buffer));
36     strcpy(buffer,"
this is client!\n");
37     send(connfd, buffer, 1024, 0
);38
while(1)46
close(connfd);
47return0;
48 }

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