【linux高级程序设计】（第十四章）TCP高级应用 3

时间：2015-08-04 20:49:00 阅读：202 评论：0 收藏：0 [点我收藏+]

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控制socket文件描述符属性

1.set/getsockopt()修改socket属性

int getsockopt (int __fd, int __level, int __optname, void *__restrict __optval, socklen_t *__restrict __optlen)：获得某个套接字的属性。成功0，失败-1

int setsockopt (int __fd, int __level, int __optname, __const void *__optval, socklen_t __optlen) ：设置某个套接字属性

参数1：套接字描述符。

参数2：指定套接字属性的分类，标识某个协议级别

#define SOL_SOCKET   1    //通用套接字选项
#define IPPROTO_IP   0    //IP选项
#define IPPROTO_TCP  6    //TCP选项

参数3：指定控制的参数，在参数2不同的情况下有不同选项

SOL_SOCKET的选项如下：

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IPPROTO_IP选项如下：

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IPPROTO_TCP选项如下：

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参数4：套接字选项值，根据选项名称的数据类型进行转换

参数5：缓冲区大小，返回时为反向的值的长度。

例子：列出某个socket对象的基本信息

#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<string.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<netinet/tcp.h>
#include<sys/socket.h>
#include<sys/wait.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/time.h>
int main(int argc, char *argv[])
{
    int rcvbuf_size;
    int sndbuf_size;
    int type = 0;
    socklen_t size;
    int sock_fd;
    struct timeval set_time, ret_time;
    if((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket");
        exit(EXIT_FAILURE);
    }
    //获取发送缓冲区大小
    size = sizeof(sndbuf_size);
    getsockopt(sock_fd, SOL_SOCKET, SO_SNDBUF, &sndbuf_size, &size);
    printf("sndbuf_size = %d\n", sndbuf_size);
    //获取接收缓冲区大小
    size = sizeof(rcvbuf_size);
    getsockopt(sock_fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf_size, &size);
    printf("rcvbuf_size = %d\n", rcvbuf_size);
    //获取socket类型
    size = sizeof(type);
    getsockopt(sock_fd, SOL_SOCKET, SO_TYPE, &type, &size);
    printf("type = %d\n", type);
    //获取发送超时值
    size = sizeof(struct timeval);
    getsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, &ret_time, &size);
    printf("default: time out is %ds and %dus\n", ret_time.tv_sec, ret_time.tv_usec);
    //修改超时值
    set_time.tv_sec = 10;
    set_time.tv_usec = 100;
    setsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, &set_time, size);
    getsockopt(sock_fd, SOL_SOCKET, SO_SNDTIMEO, &ret_time, &size);
    printf("after modify: time out is %ds and %dus\n", ret_time.tv_sec, ret_time.tv_usec);
    //读取TTL值
    int ttl = 0;
    size = sizeof(ttl);
    getsockopt(sock_fd, IPPROTO_IP, IP_TTL, &ttl, &size);
    printf("the default ip ttl is %d\n", ttl);
    //读取TCP_MAXSEG值
    int maxseg = 0;
    size = sizeof(maxseg);
    getsockopt(sock_fd, IPPROTO_TCP, TCP_MAXSEG, &maxseg, &size);
    printf("the TCP max seg is %d\n", maxseg);
}

效果

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2.fcntl控制socket

1.控制socket为非阻塞方式

int flags;
if((flags = fcntl(fd, F_GETFL, 0)) < 0)
{
    perror("fcntl");
    exit(EXIT_FAILURE);
}
flags |= O_NONBLOCK;
if(fcntl(fd, F_SETFL, flags) < 0)
{
    perror("fcntl");
    exit(EXIT_FAILURE);
}

2.设置socket为信号驱动型。socket状态改变时产生SIGIO信号

int flags;
if((flags = fcntl(fd, F_GETFL, 0)) < 0)
{
    perror("fcntl");
    exit(EXIT_FAILURE);
}
flags |= O_ASYNC;
if(fcntl(fd, F_SETFL, flags) < 0)
{
    perror("fcntl");
    exit(EXIT_FAILURE);
}