socket_server.c

Linux下C语言编程例子

#include<sys/types.h>
#include<sys/socket.h>
#include<sys/time.h>
#include<sys/ioctl.h>
#include<stdio.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>

void exec_command(int c_sockfd) 
/* exec_command()负责在与服务器连接成功后传送指令并显示结果。 */

{
    char buf[256];	/* 用于处理输入的缓冲区 */
    int n;
	
    /* 把stdout和stderr重定向到sockfd */	
    close(1);
    dup(c_sockfd);
    close(2);
    dup(c_sockfd);
    
    n = read(c_sockfd, buf, sizeof(buf));
    
    if (n > 0) {
    	
	//printf("%d server %s", n, buf);
	system(buf);
    }
}

int main()
{
    int server_sockfd, client_sockfd;
    int client_len;
    struct sockaddr_in server_address;
    struct sockaddr_in client_address;
    //char buf[BUFSIZ];
    int result;
    fd_set readfds, testfds;

    server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = htonl(INADDR_ANY);
    server_address.sin_port = htons(19734);
    client_len = sizeof(client_address);

    bind(server_sockfd, (struct sockaddr *) &server_address, sizeof(server_address));
    
    listen(server_sockfd, 5);
    FD_ZERO(&readfds);
    FD_SET(server_sockfd, &readfds);
    
    while (1) {
    	char ch;
	int fd;
	static int max_fd = 10;	/* 为了节省资源，这里最大只使用了10个文件描述符。 */
	int n;
	
	testfds = readfds;
	printf("server waiting\n");
		
	result = select(max_fd, &testfds, (fd_set *)0, (fd_set *)0, (struct timeval *)0);
	
	if(result < 1) {		/* 如果小于1 ，说明select执行出错。 */
		perror("server");
		exit(1);
	}
	
	for(fd = 0; fd < max_fd; fd++) {
		
		if(FD_ISSET(fd, &testfds)) {
			//printf("checking%d serverfd%d", fd, server_sockfd);
			if(fd == server_sockfd) {	/* 如果是来自server，则产生新的连接。 */
				client_sockfd = accept(server_sockfd, (struct sockaddr *) &client_address, &client_len);
				FD_SET(client_sockfd, &readfds);
				if(client_sockfd > max_fd) max_fd = client_sockfd;
				printf("adding client on fd %d\n",client_sockfd);
			}
			else {	/* 检查有没有输入，如果没有，则关闭连接； 如果有，则执行命令。 */
				ioctl(fd, FIONREAD, &n);
				
				if(n == 0) {
					close(client_sockfd);
					FD_CLR(fd, &readfds);
					printf("removing client on fd %d\n", fd);
				}
				else {
					exec_command(fd); /* 处理通信的内容 */
					//printf("exec_fd:%d\n", fd);
				}
			}
			
		}
	}
    }
}