非阻塞I/O事件处理

　　本节所使用的方式是将非阻塞式I/O与I/O多路复用结合，采用类似事件出发的机制对I/O操作进行处理；与多进程和多线程技术相比，异步I/O技术的最大优势是系统开销小，系统不必创建进程/线程，也不必维护这些进程/线程，从而减少了系统的开销。

 1 /**
 2   client.c
 3 */
 4 #include <stdio.h>
 5 #include <unistd.h>
 6 #include <string.h>
 7 #include <strings.h>
 8 #include <sys/types.h>
 9 #include <sys/socket.h>
10 #include <netinet/in.h>
11 #include <arpa/inet.h>
12 
13 #define PORT 8111
14 #define MSG_LEN 1024
15 
16 int main(int argc, char* argv[])
17 {
18     if (argc != 2) {
19         printf("usage: ./%s <ipaddress>
", argv[0]);
20         return 1;
21     }
22     
23     int ret = -1;
24     int socket_fd;
25     socklen_t addr_len;
26     struct sockaddr_in serv_addr;
27     char send_buf[MSG_LEN] = { 0 };
28     char recv_buf[MSG_LEN] = { 0 };
29 
30     socket_fd = socket(AF_INET, SOCK_STREAM, 0);
31     if (socket_fd < 0) {
32         printf("create socket fd failed.
");
33         _exit(-1);
34     }
35 
36     bzero(&serv_addr, sizeof(serv_addr));
37     serv_addr.sin_family = AF_INET;
38     serv_addr.sin_port = htons(PORT);
39     serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
40     addr_len = sizeof(struct sockaddr);
41     ret = connect(socket_fd, (struct sockaddr *)&serv_addr, addr_len);
42     if (ret < 0) {
43         printf("connect to server[%s:%d] failed.
", argv[1], PORT);
44         _exit(-1);
45     }
46 
47     while (1) {
48         memset(send_buf, 0, sizeof(send_buf));
49         memset(recv_buf, 0, sizeof(recv_buf));
50         gets(send_buf);
51         
52         if (strncmp(send_buf, "quit", 4) == 0)
53             break;
54 
55         ret = send(socket_fd, (void *)send_buf, strlen(send_buf), 0);
56         if (ret < 0) {
57             printf("send msg[%s] failed.
", send_buf);
58             break;
59         }
60         
61         ret = recv(socket_fd, (void *)recv_buf, sizeof(recv_buf), 0);
62         if (ret < 0) {
63             printf("receive zero msg.
");
64             continue;
65         }
66 
67         recv_buf[ret] = '

非阻塞I/O事件处理

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