并发服务器select

思想：

用select管理多个IO，一旦其中一个IO或者多个IO检测到我们感兴趣的时间，select函数返回，返回值为检测到的事件个数。并且会返回哪些IO发生了事件，遍历这些事假然后处理它。

函数

int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
[1] nfds表示存放到这些集合的描述符的最大值加1，比如readfds存的是3，5，8，write中存放的是4，9，exception填空指针，那么此时最大描述符为9，那么nfds就是10。
[2] readfds，读集合
发生条件：
1) 套接口缓冲区有数据刻度
2) 套接口的读一半关闭，解接收FIN段，读操作返回0
3) 如果是监听套接口，已完成连接队列不为空时
4) 套接口上发生了一个错误待处理，错误可通过getstock指定SO_ERROR选项来获取
[3] writefds，写集合
发生条件：
1) 套接口发送缓冲区有空间接纳数据
2) 连接的写一半关闭，即接收到RST段之后，再次调用write操作，此时会产生SIGPIPE信号
3) 套接口上发生了一个错误待处理，错误可通过getstock指定SO_ERROR选项来获取
[4] 异常集合
发生条件：
1) 套接口存在外带数据
[5] 超时时间结构体
void FD_CLR(int fd, fd_set *set)，将文件描述符从集合中移除
int FD_ISEET(int fd, fd_set *set)，判断文件描述符是否在集合中，用来判断对应的文件描述符发生了变化
void FD_SET(int fd, fd_set *set)，将文件描述符添加到集合中

void FD_ZERO(fd_set *set)，清空集合

问题

select会受到FD_SETSIZE的限制，监听的端口会有限，因为select本质是轮训模式，如果监听的端口比较多，那么效率可能会很低，因此端口数量不能很多。

服务器端：

#include<unistd.h>#include<sys/types.h>#include<sys/socket.h>#include<netinet/in.h>#include<arpa/inet.h>#include<sys/wait.h>#include<stdlib.h>#include<stdio.h>#include<errno.h>#include<string.h>#include<signal.h>#define ERR_EXIT(m) do{perror(m);exit(EXIT_FAILURE);}while(1)struct packet{int len;char buf[1024];};ssize_t readn(int fd, void *buf, size_t count){size_t nleft = count;ssize_t nread;char *bufp = (char*)buf;while (nleft > 0){if ((nread = read(fd, bufp, nleft)) < 0){if (errno == EINTR){continue;return -1;}else if (nread == 0)return count - nleft;}bufp = bufp + nread;nleft = nleft - nread;}return count;}ssize_t writen(int fd, void *buf, size_t count){size_t nleft = count;ssize_t nwrite;char *bufp = (char*)buf;while (nleft > 0){if ((nwrite = write(fd, bufp, nleft)) < 0){if (errno == EINTR){continue;return -1;}else if (nwrite == 0)continue;}bufp = bufp + nwrite;nleft = nleft - nwrite;}return count;}ssize_t recv_peek(int sockfd, void *buf, size_t len){while (1){int ret = recv(sockfd, buf, len, MSG_PEEK);if (ret == -1 && errno == EINTR)continue;return ret;}}ssize_t readline(int sockfd, void *buf, size_t maxline){int ret;int nread;char *bufp = (char*)buf;int nleft = maxline;while (1){ret = recv_peek(sockfd, bufp, nleft);if (ret < 0)return ret;else if (ret == 0)return ret;//对方关闭了套接口nread = ret;for (int i = 0; i < nread; i++){if (bufp[i] == '\n'){ret = readn(sockfd, bufp, i + 1);//将缓冲区数据移除if (ret != i + 1)exit(EXIT_FAILURE);return ret;}}if (nread>nleft)exit(EXIT_FAILURE);//读到的数据不能超过缓冲区nleft -= nread;ret = readn(sockfd, bufp, nread);if (ret != nread)exit(EXIT_FAILURE);bufp += nread;}return -1;}void do_service(int connfd){char recvbuf[1024];int n;while (1){memset(&recvbuf, 0, sizeof(recvbuf));int ret = readline(connfd, recvbuf, 1204);if (ret == -1){ERR_EXIT("read");}else if (ret == 0){printf("client cloase\n");break;}fputs(recvbuf, stdout);writen(connfd, recvbuf, strlen(recvbuf));}}void handle_sigchild(int sig){//  wait(NULL);   while(waitpid(-1,NULL,WNOHANG)>0);//}int main(void){//signal(SIGCHLD, SIG_IGN);signal(SIGCHLD,handle_sigchild);        int listenfd;if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)ERR_EXIT("socket");struct sockaddr_in servaddr;memset(&servaddr, 0, sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_port = htons(5188);servaddr.sin_addr.s_addr = htonl(INADDR_ANY);int on = 1;if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)ERR_EXIT("setsockopt");if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)ERR_EXIT("bind");if (listen(listenfd, SOMAXCONN) < 0)ERR_EXIT("listten");/*while (1){int connfd;struct sockaddr_in peeraddr;socklen_t peerlen = sizeof(peeraddr);if ((connfd = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen)) < 0)ERR_EXIT("accept");printf("ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));pid_t pid = fork();if (pid == -1)ERR_EXIT("fork");if (pid == 0){close(listenfd);do_service(connfd);exit(EXIT_SUCCESS);}if (pid > 0){close(connfd);}}*/int client[FD_SETSIZE];//最大处理的数量for (int i = 0; i < FD_SETSIZE; i++)client[i] = -1;int nready = 0;    int maxi=0;//最大空闲描述符int maxfd = listenfd;//因为此时并没有新的进来，因此此时最大的就是监听套接字fd_set rset, allset;FD_ZERO(&rset);FD_ZERO(&allset);FD_SET(listenfd, &allset);while (1){rset = allset;//因为每次监听后，rset里面的内容会改变nready = select(maxfd + 1, &rset, NULL, NULL, NULL);if (nready == -1){if (errno == EINTR)continue;//被信号中断ERR_EXIT("select");}if (nready == 0)continue;if (FD_ISSET(listenfd, &rset))//是否是监听套接口产生了事件{int connfd;struct sockaddr_in peeraddr;socklen_t peerlen = sizeof(peeraddr);if ((connfd = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen)) < 0)ERR_EXIT("accept");int i = 0;for ( i = 0; i < FD_SETSIZE; i++){if (client[i] == -1){client[i] = connfd;//找到空闲位置        if(i>maxi)maxi=i;                                 break;}}if (i == FD_SETSIZE){printf("server is full, too many client\n");exit(EXIT_FAILURE);}printf("ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));FD_SET(connfd, &allset);maxfd = maxfd>connfd ? maxfd : connfd;if (--nready <= 0)continue;//检测到的事件已经处理完了}for (int i = 0; i <= maxi; i++){int connfd = client[i];if (connfd == -1)continue;if (FD_ISSET(connfd, &rset))//判断是否发生了读事件{//printf("reading.........\n");char recvbuf[1024];memset(&recvbuf, 0, sizeof(recvbuf));int ret = readline(connfd, recvbuf, sizeof(recvbuf));if (ret == -1){ERR_EXIT("read");}else if (ret == 0){printf("client close\n");FD_CLR(connfd, &allset);//套接字已经关闭，从集合中清除               client[i]=-1;//设置为空闲                }fputs(recvbuf, stdout);writen(connfd, recvbuf, strlen(recvbuf));if (--nready <= 0)break;//检测到的事件已经处理完了,重新监听}}}close(listenfd);}

客户端：

#include<unistd.h>#include<sys/types.h>#include<sys/socket.h>#include<netinet/in.h>#include<arpa/inet.h>#include<stdlib.h>#include<stdio.h>#include<errno.h>#include<string.h>#define ERR_EXIT(m) do{perror(m);exit(EXIT_FAILURE);}while(0)struct packet{int len;char buf[1024];};ssize_t readn(int fd, void *buf, size_t count){size_t nleft = count;ssize_t nread;char *bufp = (char*)buf;while (nleft > 0){if ((nread = read(fd, bufp, nleft)) < 0){if (errno == EINTR){continue;return -1;}else if (nread == 0)return count - nleft;}bufp = bufp + nread;nleft = nleft - nread;}return count;}ssize_t writen(int fd, void *buf, size_t count){size_t nleft = count;ssize_t nwrite;char *bufp = (char*)buf;while (nleft > 0){if ((nwrite = write(fd, bufp, nleft)) < 0){if (errno == EINTR){continue;return -1;}else if (nwrite == 0)continue;}bufp = bufp + nwrite;nleft = nleft - nwrite;}return count;}ssize_t recv_peek(int sockfd, void *buf, size_t len){while (1){int ret = recv(sockfd, buf, len, MSG_PEEK);if (ret == -1 && errno == EINTR)continue;return ret;}}ssize_t readline(int sockfd, void *buf, size_t maxline){int ret;int nread;char *bufp = (char*)buf;int nleft = maxline;while (1){ret = recv_peek(sockfd, bufp, nleft);if (ret < 0)return ret;else if (ret == 0)return ret;//对方关闭了套接口nread = ret;for (int i = 0; i < nread; i++){if (bufp[i] == '\n'){ret = readn(sockfd, bufp, i + 1);//将缓冲区数据移除if (ret != i + 1)exit(EXIT_FAILURE);return ret;}}if (nread>nleft)exit(EXIT_FAILURE);//读到的数据不能超过缓冲区nleft -= nread;ret = readn(sockfd, bufp, nread);if (ret != nread)exit(EXIT_FAILURE);bufp += nread;}return -1;}void echo_cli(int sockfd){char sendbuf[1024];char recvbuf[1024];memset(sendbuf, 0, sizeof(sendbuf));memset(recvbuf, 0, sizeof(recvbuf));while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL){writen(sockfd, sendbuf, strlen(sendbuf));int ret = readline(sockfd, recvbuf, sizeof(recvbuf));if (ret == -1)ERR_EXIT("read");if (ret == 0){printf("server close\n");break;}fputs(recvbuf, stdout);memset(sendbuf, 0, sizeof(sendbuf));memset(recvbuf, 0, sizeof(recvbuf));}close(sockfd);}void echo_cli1(int sockfd){fd_set rset;FD_ZERO(&rset);int nready;int maxfd;int fd_stdin = fileno(stdin);if (fd_stdin > sockfd)maxfd = fd_stdin;else maxfd = sockfd;char sendbuf[1024];char recvbuf[1024];while (1){FD_SET(fd_stdin, &rset);FD_SET(sockfd, &rset);nready = select(maxfd + 1, &rset, NULL, NULL, NULL);if (nready == -1)ERR_EXIT("select");if (nready == 0)continue;if (FD_ISSET(sockfd, &rset)){int ret = readline(sockfd, recvbuf, sizeof(recvbuf));if (ret == -1)ERR_EXIT("read");if (ret == 0){printf("server close\n");break;}fputs(recvbuf, stdout);}if (FD_ISSET(fd_stdin, &rset)){if (fgets(sendbuf, sizeof(sendbuf), stdin) == NULL)break;writen(sockfd, sendbuf, strlen(sendbuf));}memset(sendbuf, 0, sizeof(sendbuf));memset(recvbuf, 0, sizeof(recvbuf));}close(sockfd);}int main(void){int sockfd;if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)ERR_EXIT("socket");struct sockaddr_in servaddr;memset(&servaddr, 0, sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_port = htons(5188);servaddr.sin_addr.s_addr = inet_addr("127.0.1");if (connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)ERR_EXIT("bind");echo_cli1(sockfd);}