linux socket小例

/*socket select模型，服务端绝大多数注释自己写的，参考man*/#include <sys/types.h>#include <sys/socket.h>#include <sys/wait.h>#include <stdio.h>#include <stdlib.h>#include <errno.h>#include <string.h>#include <sys/un.h>#include <sys/time.h>#include <sys/ioctl.h>#include <unistd.h>#include <netinet/in.h>#define SERVPORT 3333#define BACKLOG 10#define MAX_CONNECTED_NO 10#define MAXDATASIZE 100int main(){/* struct sockaddr_in { //地址族AF_INET（IPv4）AF_INET6（IPv6）AF_LOCAL（UNIX域协议）AF_LINK（链路地址协议）AF_KEY（密钥套接字socket）AF_APPLETALK（ddp）　　 short int sin_family;//端口号　　 unsigned short int sin_port;**struct in_addr { *unsigned long s_addr;*}*//地址struct in_addr sin_addr; unsigned char sin_zero[8];} eg:struct sockaddr_in ina;bzero(&ina,sizeof(ina));ina.sin_family=AF_INET;ina.sin_port=htons(23);ina.sin_addr.s_addr = inet_addr("132.241.5.10"); AF_INET和PF_INET略有差异 */struct sockaddr_in server_sockaddr,client_sockaddr;int sin_size,recvbytes;fd_set readfd;fd_set writefd;int sockfd,client_fd;char buf[MAXDATASIZE];/*int socket(int domain, int type, int protocol);domain:PF_INET...type:SOCK_STREAM,SOCK_STREAM,SOCK_RAW...protocol:/etc/protocols tcp,udp...*/if((sockfd = socket(AF_INET,SOCK_STREAM,0))==-1){perror("socket");exit(1);}printf("socket success!,sockfd=%d/n",sockfd);server_sockaddr.sin_family=AF_INET;server_sockaddr.sin_port=htons(SERVPORT);server_sockaddr.sin_addr.s_addr=INADDR_ANY;//set to 0bzero(&(server_sockaddr.sin_zero),8);/*int bind(int sockfd, const struct sockaddr *my_addr,socklen_t addrlen);sockfd:created by socket*my_addr:convert from sockaddr_inaddrlen:sizeof(sockaddr)*/if(bind(sockfd,(struct sockaddr *)&server_sockaddr,sizeof(struct sockaddr))==-1){perror("bind");exit(1);}printf("bind success!/n");/*int listen(int sockfd, int backlog);sockfd:created by socketbacklog:the maximum length the queue of pending connections may grow to(最多接受的connect数)*/if(listen(sockfd,BACKLOG)==-1){perror("listen");exit(1);}printf("listening..../n");/* man FD_ZERO can getFD_ZERO()clears a set. FD_SET() and FD_CLR() respectively add and remove a given file descriptor from a set*/FD_ZERO(&readfd);FD_SET(sockfd,&readfd);while(1){sin_size=sizeof(struct sockaddr_in);/*int select(int nfds, fd_set *readfds, fd_set *writefds,fd_set *exceptfds, struct timeval *timeout);nfds:the max file descriptortimeval:struct timeval {　　time_t tv_sec; // seconds 　　suseconds_t tv_usec; // microseconds }*/if(select(MAX_CONNECTED_NO,&readfd,NULL,NULL,(struct timeval *)0)>0){if(FD_ISSET(sockfd,&readfd)>0){/*int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);returns a non-negative integer that is a descriptor for the accepted socket*/if((client_fd=accept(sockfd,(struct sockaddr *)&client_sockaddr,&sin_size))==-1){perror("accept");exit(1);}/*ssize_t recv(int s, void *buf, size_t len, int flags);flag:most is zero*/if((recvbytes=recv(client_fd,buf,MAXDATASIZE,0))==-1){perror("recv");exit(1);}if(read(client_fd,buf,MAXDATASIZE)<0){perror("read");exit(1);}printf("received a connection :%s",buf);}/*if*/close(client_fd);}/*select*/}/*while*/}