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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_REUSEADDR 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); - 1
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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; } - 1
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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; } - 1
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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; } - 1
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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);- 1
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; } - 1
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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; } - 1
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socket.c
#include "net.h" void Argment(int argc, char *argv[]){ if(argc < 3){ fprintf(stderr, "%s\n" - 1
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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 - 1
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通过wireshark查看设置keepalive的包
6 练习
编程实现带保活连接功能的TCP代码，要求开始首次KeepAlive探测前的TCP空闭时间为3秒，两次KeepAlive探测间的时间间隔为3次，判定断开前的KeepAlive探测次数为7次。提交代码和完成通信的截图
注意：部分操作系统需要添加额外头文件 netinet/tcp.h#include#include #include #include #include #include #include #include #include #include #define MAX_SOCK_FD 1024 #define BACKLOG 5 #define ErrExit(msg) do{perror(msg); exit(EXIT_FAILURE);} while(0) 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 DataHandle(int fd) { char buf[BUFSIZ] = {}; int ret; struct sockaddr_in peeraddr; socklen_t peerlen = sizeof(struct sockaddr_in); if(getpeername(fd, (struct sockaddr *)&peeraddr, &peerlen) ) perror("getpeername"); 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; } int main(int argc,char *argv[]) { int fd, new_fd, i ,ret; fd_set set, tmpset; struct sockaddr_in addr, client_addr; socklen_t clientlen = sizeof(client_addr); int flag = 1; if(argc < 3) { printf("%s \n",argv[0]); exit(0); } //create socket fd = socket(AF_INET, SOCK_STREAM, 0); if(fd < 0) { ErrExit("socket"); } //avoids the error of ports being occupied if( setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag) ) ) { perror("setsockopt"); } //init struct sockaddr_in memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; addr.sin_port = htons( atoi(argv[2])); if (inet_aton(argv[1], &addr.sin_addr) == 0) { printf("Invalid address\n"); exit(EXIT_FAILURE); } //bind if(bind(fd, (struct sockaddr *) &addr, sizeof(struct sockaddr_in)) == -1) { ErrExit("bind"); } //listen if(listen(fd, BACKLOG) == -1) { ErrExit("listen"); } //select 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) { ErrExit("select"); } if(FD_ISSET(fd, &tmpset) > 0) { new_fd = accept(fd,(struct sockaddr *)&client_addr,&clientlen); if(new_fd < 0) { perror("accept"); } #if 1 int keepAlive = 1; int keepIdle = 3; int keepInterval = 3; int keepCount = 7; SetKeepAlive(new_fd, keepAlive, keepIdle, keepInterval, keepCount); #endif printf("[%s:%d]connected\n",inet_ntoa(client_addr.sin_addr),\ ntohs(client_addr.sin_port)); FD_SET(new_fd, &set); } else //if(FF_ISSET(fd, &tmpset < 0) //handle client { for(i = fd + 1; i < MAX_SOCK_FD; i++) { // can read if(FD_ISSET(i,&tmpset)) { if(DataHandle(i) <= 0) { if(getpeername(i,(struct sockaddr *)&client_addr,&clientlen)) perror("getpeername"); printf("[%s:%d]disconnected\n",inet_ntoa(client_addr.sin_addr),\ ntohs(client_addr.sin_port)); FD_CLR(i,&set); } } } } } close(fd); return 0; } - 1
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- 原文地址：https://blog.csdn.net/m0_60718520/article/details/133802481