lv8 嵌入式开发-网络编程开发 17 套接字属性设置

1 基本概念

• 设置套接字的选项对套接字进行控制
• 除了设置选项外，还可以获取选项
• 选项的概念相当于属性，所以套接字选项也可说是套接字属性
• 有些选项（属性）只可获取，不可设置；
• 有些选项既可设置也可获取

2 选项的级别

一些选项都是针对一种特定的协议
一些选项适用于所有类型的套接字
选项级别(level)的概念

2.1 常用的级别

SOL_SOCKET	该级别的选项只作用于套接字本身
SOL_LRLMP	该级别的选项作用于IrDA协议
IPPROTO_IP	该级别的选项作用于IPv4协议
IPPROTO_IPV6	该级别的选项作用于IPv6协议
IPPROTO_RM	该级别的选项作用于可靠的多播传输
IPPROTO_TCP	该级别的选项适用于流式套接字
IPPROTO_UDP	该级别的选项适用于数据报套接字

2.2 SOL_SOCKET的常用选项

选项名称	说明	获取/设置
SO_ACCEPTCONN	套接字是否处于监听状态	获取
SO_BROADCAST	允许发送广播数据	两者都可
SO_DEBUG	允许调试	两者都可
SO_DONTROUTE	不查找路由	两者都可
SO_ERROR	获得套接字错误	获取
SO_KEEPALIVE	保活连接	两者都可
SO_LINGER	延迟关闭连接	两者都可
SO_OOBINLINE	带外数据放入正常数据流	两者都可
SO_RCVBUF	接收缓冲区大小	两者都可
SO_SNDBUF	发送缓冲区大小	两者都可
SO_REUSERADDR	允许重用本地地址和端口	两者都可
SO_TYPE	获得套接字类型	获取

2.3 IPPROTO_IP级别的常用选项

选项名称	说明	获取/设置
IP_OPTIONS	获取或设置IP头部内的选项	两者都可
IP_HDRINCL	是否将IP头部与数据一起提交给Winsock函数	两者都可
IP_TTL	IP TTL相关	两者都可

3获取套接字选项

3.1 getsockopt函数

#include           /* See NOTES */
#include 
int getsockopt(int sockfd, int level, int optname, void *optval, socklen_t *optlen);

参数
sockfd：套接字描述符
level：表示选项的级别
optname：表示要获取的选项名称
optval：指向存放接收到的选项内容的缓冲区
optlen：指向optval所指缓冲区的大小
函数返回值：
执行成功返回0，否则返回‒1，errno来获取错误码
常见的错误码：
EBADF：参数sockfd不是有效的文件描述符
EFAULT：参数optlen太小或optval所指缓冲区非法
EINVAL：参数level未知或非法
ENOPROTOOPT：选项未知或不被指定的协议族所支持
ENOTSOCK：描述符不是一个套接字描述符

3.2 示例：获取流套接字和数据报套接字接收和发送的（内核）缓冲区大小

#include 
#include 
#include           
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
int main()
{
	int err,s = socket(AF_INET, SOCK_STREAM, 0);//创建流套接字
	if (s == -1) {
		printf("Error at socket()\n");
		return -1;
	}
	int su = socket(AF_INET, SOCK_DGRAM, 0); //创建数据报套接字
	if (s == -1) {
		printf("Error at socket()\n");
		return -1;
	}

	int optVal;
	int optLen = sizeof(optVal);
	//获取流套接字接收缓冲区大小
	if (getsockopt(s, SOL_SOCKET, SO_RCVBUF, (char*)&optVal,
                   (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else
		printf("Size of stream socket receive buffer: %ld bytes\n", optVal);
	//获取流套接字发送缓冲区大小
	if (getsockopt(s, SOL_SOCKET, SO_SNDBUF, (char*)&optVal,
                   (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else 
		printf("Size of streaming socket send buffer: %ld bytes\n", optVal);

	//获取数据报套接字接收缓冲区大小
	if (getsockopt(su, SOL_SOCKET, SO_RCVBUF, (char*)&optVal,
                   (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else
		printf("Size of datagram socket receive buffer: %ld bytes\n", optVal);
	//获取数据报套接字发送缓冲区大小
	if (getsockopt(su, SOL_SOCKET, SO_SNDBUF, (char*)&optVal,
                   (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else
		printf("Size of datagram socket send buffer:%ld bytes\n", optVal);

	getchar();
	return 0;
}

3.3 示例：获取当前套接字类型

#include 
#include 
#include 
#include           
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main()
{
	int err;
	int s = socket(AF_INET, SOCK_STREAM, 0); //创建流套接字
	if (s == -1) {
		printf("Error at socket()\n");
		return -1;
	}
	int su = socket(AF_INET, SOCK_DGRAM, 0); //创建数据报套接字
	if (s == -1) {
		printf("Error at socket()\n");
		return -1;
	}

	int optVal;
	int optLen = sizeof(optVal);
	//获取套接字s的类型
	if (getsockopt(s, SOL_SOCKET, SO_TYPE, (char*)&optVal, (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else
	{
		if (SOCK_STREAM == optVal) // SOCK_STREAM宏定义值为1
			printf("The current socket is a stream socket.\n"); //当前套接字是流套接字
		else if (SOCK_DGRAM == optVal) // SOCK_ DGRAM宏定义值为2
			printf("The current socket is a datagram socket.\n");//当前套接字是数据报套接字
	}
	//获取套接字su的类型
	if (getsockopt(su, SOL_SOCKET, SO_TYPE, (char*)&optVal, (socklen_t *)&optLen) == -1)
		printf("getsockopt failed:%d", errno);
	else
	{
		if (SOCK_STREAM == optVal)  // SOCK_STREAM宏定义值为1
			printf("The current socket is a stream socket.\n");
		else if (SOCK_DGRAM == optVal) // SOCK_ DGRAM宏定义值为2
			printf("The current socket is a datagram socket.\n");
	}
	getchar();
	return 0;
}

3.4 示例：判断套接字是否处于监听状态

#include 
#include 
#include 
#include 
#include           
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;

#define ErrExit(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)

int main(int argc, char *argv[])
{
        Addr_in service;
        if(argc < 3)
        {
                printf("%s[ADDR][PORT]\n", argv[0]);
                exit(0);
        }
        int s = socket(AF_INET, SOCK_STREAM, 0); //创建一个流套接字
        if (s == -1) 
                ErrExit("socket");
        //允许地址的立即重用
        char on = 1;
        setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

        service.sin_family = AF_INET;
        service.sin_addr.s_addr = inet_addr(argv[1]);
        service.sin_port = htons( atoi(argv[2]) );
        if (bind(s, (Addr*)&service, sizeof(service)) == -1) //绑定套接字
                ErrExit("bind");
        int optVal;
        int optLen = sizeof(optVal);
        //获取选项SO_ACCEPTCONN的值
        if (getsockopt(s, SOL_SOCKET, SO_ACCEPTCONN, (char*)&optVal, (socklen_t*)&optLen) == -1)
                printf("getsockopt failed:%d",errno);
        else printf("Before listening, The value of SO_ACCEPTCONN:%d, The socket is not listening\n", optVal);

        // 开始侦听
        if (listen(s, 100) == -1)
                ErrExit("listen");
        //获取选项SO_ACCEPTCONN的值
        if (getsockopt(s, SOL_SOCKET, SO_ACCEPTCONN, (char*)&optVal, (socklen_t*)&optLen) == -1)
                ErrExit("getsockopt");
        else printf("After listening,The value of SO_ACCEPTCONN:%d, The socket is listening\n", optVal);
        return 0;
}

4 设置套接字选项

4.1 setsockopt函数

int setsockopt(int sockfd, int level, int optname, const void *optval, socklen_t optlen);

参数
sockfd：套接字描述符
level：表示选项的级别
optname：表示要获取的选项名称
optval：指向存放接收到的选项内容的缓冲区
optlen：指向optval所指缓冲区的大小
函数返回值：
执行成功返回0，否则返回‒1，errno来获取错误码

4.2 示例：启用套接字的保活机制**

#include 
#include 
#include 
#include 
#include           
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;

#define ErrExit(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)

int main(int argc, char *argv[])
{
        Addr_in service;
        if(argc < 3)
        {
                printf("%s[ADDR][PORT]\n", argv[0]);
                exit(0);
        }

        int s = socket(AF_INET, SOCK_STREAM, 0); //创建一个流套接字
        if( s < 0)
                ErrExit("socket");

        char on = 1;
        setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

        service.sin_family = AF_INET;
        service.sin_addr.s_addr = inet_addr(argv[1]);
        service.sin_port = htons(atoi(argv[2]));
        if (bind(s, (Addr *) &service, sizeof(service)) == -1) //绑定套接字
                ErrExit("bind");

        int optVal = 1;//一定要初始化
        int optLen = sizeof(int);

        //获取选项SO_KEEPALIVE的值
        if (getsockopt(s, SOL_SOCKET, SO_KEEPALIVE, (char*)&optVal, (socklen_t *)&optLen) == -1)
                ErrExit("getsockopt");
        else printf("After listening,the value of SO_ACCEPTCONN:%d\n", optVal);

        optVal = 1;
        if (setsockopt(s, SOL_SOCKET, SO_KEEPALIVE, (char*)&optVal, optLen) != -1)
                printf("Successful activation of keep alive mechanism.\n");//启用保活机制成功

        if (getsockopt(s, SOL_SOCKET, SO_KEEPALIVE, (char*)&optVal, (socklen_t *)&optLen) == -1)
                ErrExit("getsockopt");
        else printf("After setting,the value of SO_KEEPALIVE:%d\n", optVal);

        return 0;
}

5 综合示例

server.c

#include "net.h"
#include 
#define MAX_SOCK_FD 1024

void setKeepAlive (int sockfd, int attr_on, socklen_t idle_time, socklen_t interval, socklen_t cnt)
{
	setsockopt (sockfd, SOL_SOCKET, SO_KEEPALIVE, (const char *) &attr_on, sizeof (attr_on));
	setsockopt (sockfd, SOL_TCP, TCP_KEEPIDLE, (const char *) &idle_time, sizeof (idle_time));
	setsockopt (sockfd, SOL_TCP, TCP_KEEPINTVL, (const char *) &interval, sizeof (interval));
	setsockopt (sockfd, SOL_TCP, TCP_KEEPCNT, (const char *) &cnt, sizeof (cnt));
}

int main(int argc, char *argv[])
{
	int i, ret, fd, newfd;
	fd_set set, tmpset;
	Addr_in clientaddr;
	socklen_t clientlen = sizeof(Addr_in);
	/*检查参数，小于3个 直接退出进程*/
	Argment(argc, argv);
	/*创建已设置监听模式的套接字*/
	fd = CreateSocket(argv);

	FD_ZERO(&set);
	FD_ZERO(&tmpset);
	FD_SET(fd, &set);
	while(1){
		tmpset = set;
		if( (ret = select(MAX_SOCK_FD, &tmpset, NULL, NULL, NULL)) < 0){
			perror("select");
			getchar();
		}
		if(FD_ISSET(fd, &tmpset) ){
			/*接收客户端连接，并生成新的文件描述符*/
			if( (newfd = accept(fd, (Addr *)&clientaddr, &clientlen) ) < 0){
				perror("accept");
				getchar();
			}
#if 1
			int keepAlive = 1;			//设定KeepAlive
			int keepIdle = 5;			//开始首次KeepAlive探测前的TCP空闭时间
			int keepInterval = 5;		//两次KeepAlive探测间的时间间隔
			int keepCount = 3;			//判定断开前的KeepAlive探测次数
			setKeepAlive (newfd, keepAlive, keepIdle, keepInterval, keepCount);
#endif

			printf("[%s:%d]已建立连接\n", 
					inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));
			FD_SET(newfd, &set);
		}else{ //处理客户端数据
			for(i = fd + 1; i < MAX_SOCK_FD; i++){
				if(FD_ISSET(i, &tmpset)){
					if( DataHandle(i) <= 0){
						if( getpeername(i, (Addr *)&clientaddr, &clientlen) )
							perror("getpeername");
						printf("[%s:%d]断开连接\n", 
								inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));
						FD_CLR(i, &set);
						close(i);
					}
				}
			}
		}
	}
	close(fd);
	return 0;
}

socket.c

#include "net.h"

void Argment(int argc, char *argv[]){
	if(argc < 3){
		fprintf(stderr, "%s\n", argv[0]);
		exit(0);
	}
}
int CreateSocket(char *argv[]){
	/*创建套接字*/
	int fd = socket(AF_INET, SOCK_STREAM, 0);
	if(fd < 0)
		ErrExit("socket");
	/*允许地址快速重用*/
	int flag = 1;
	if( setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag) ) )
		perror("setsockopt");
	/*设置通信结构体*/
	Addr_in addr;
	bzero(&addr, sizeof(addr) );
	addr.sin_family = AF_INET;
	addr.sin_port = htons( atoi(argv[2]) );
	/*绑定通信结构体*/
	if( bind(fd, (Addr *)&addr, sizeof(Addr_in) ) )
		ErrExit("bind");
	/*设置套接字为监听模式*/
	if( listen(fd, BACKLOG) )
		ErrExit("listen");
	return fd;
}
int DataHandle(int fd){
	char buf[BUFSIZ] = {};
	Addr_in peeraddr;
	socklen_t peerlen = sizeof(Addr_in);
	if( getpeername(fd, (Addr *)&peeraddr, &peerlen) )
		perror("getpeername");
	int ret = recv(fd, buf, BUFSIZ, 0);
	if(ret < 0)
		perror("recv");
	if(ret > 0){
		printf("[%s:%d]data: %s\n", 
				inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port), buf);
	}
	return ret;
}

net.h

`#ifndef _NET_H_
#define _NET_H_

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;
#define BACKLOG 5
#define ErrExit(msg) do { perror(msg); exit(EXIT_FAILURE); } while(0)

void Argment(int argc, char *argv[]);
int CreateSocket(char *argv[]);
int DataHandle(int fd);

#endif

通过wireshark查看设置keepalive的包