#include  <unistd.h>#include  <sys/types.h>       /* basic system data types */#include  <sys/socket.h>      /* basic socket definitions */#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */#include  <arpa/inet.h>       /* inet(3) functions */#include <sys/select.h>       /* select function*/

#include <stdlib.h>#include <errno.h>#include <stdio.h>#include <string.h>

#define MAXLINE 10240

void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset);

int  main(int argc, char **argv){int  servPort = 6888;int listenq = 1024;

int  listenfd, connfd;struct sockaddr_in cliaddr, servaddr;    socklen_t socklen = sizeof(struct sockaddr_in);int nready, nread;char buf[MAXLINE];int clientSockFds[FD_SETSIZE];    fd_set allset, rset;int maxfd;

    listenfd = socket(AF_INET, SOCK_STREAM, 0);if (listenfd < 0) {        perror("socket error");return -1;    }

int opt = 1;if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {        perror("setsockopt error");        }  

    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);    servaddr.sin_port = htons(servPort);

if(bind(listenfd, (struct sockaddr*)&servaddr, socklen) == -1) {        perror("bind error");        exit(-1);    }

if (listen(listenfd, listenq) < 0) {        perror("listen error");return -1;    }

int i = 0;for (i = 0; i< FD_SETSIZE; i++)         clientSockFds[i] = -1;     FD_ZERO(&allset);    FD_SET(listenfd, &allset);     maxfd = listenfd;    

    printf("echo server use select startup, listen on port %d\n", servPort);    printf("max connection: %d\n", FD_SETSIZE);

for ( ; ; )  {        rset = allset;        nready = select(maxfd + 1, &rset, NULL, NULL, NULL);if (nready < 0) {            perror("select error");continue;        }if (FD_ISSET(listenfd, &rset)) {            connfd = accept(listenfd, (struct sockaddr*) &cliaddr, &socklen);if (connfd < 0) {                perror("accept error");continue;            }

            sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);            printf(buf, "");

for (i = 0; i< FD_SETSIZE; i++) {if (clientSockFds[i] == -1) {                    clientSockFds[i] = connfd;break;                }            }if (i == FD_SETSIZE) {                fprintf(stderr, "too many connection, more than %d\n", FD_SETSIZE);                close(connfd);continue;            }if (connfd > maxfd)                maxfd = connfd;

            FD_SET(connfd, &allset);if (--nready <= 0)continue;        }

        handle(clientSockFds, maxfd, &rset, &allset);    }}

void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset) {int nread;int i;char buf[MAXLINE];for (i = 0; i< maxFds; i++) {if (clientSockFds[i] != -1) {if (FD_ISSET(clientSockFds[i], pRset)) {                nread = read(clientSockFds[i], buf, MAXLINE);//读取客户端socket流                if (nread < 0) {                    perror("read error");                    close(clientSockFds[i]);                    FD_CLR(clientSockFds[i], pAllset);                    clientSockFds[i] = -1;continue;                }if (nread == 0) {                    printf("client close the connection\n");                    close(clientSockFds[i]);                    FD_CLR(clientSockFds[i], pAllset);                    clientSockFds[i] = -1;continue;                } 

                write(clientSockFds[i], buf, nread);//响应客户端  有可能失败，暂不处理            }        }    }

}

#include  <unistd.h>#include  <sys/types.h>       /* basic system data types */#include  <sys/socket.h>      /* basic socket definitions */#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */#include  <arpa/inet.h>       /* inet(3) functions */#include <sys/select.h>       /* select function*/

#include <stdlib.h>#include <errno.h>#include <stdio.h>#include <string.h>

#define MAXLINE 10240#define max(a,b)    ((a) > (b) ? (a) : (b))//typedef struct sockaddr  SA;

void handle(int sockfd);

int main(int argc, char **argv){char * servInetAddr = "127.0.0.1";int servPort = 6888;char buf[MAXLINE];int connfd;struct sockaddr_in servaddr;

if (argc == 2) {        servInetAddr = argv[1];    }if (argc == 3) {        servInetAddr = argv[1];        servPort = atoi(argv[2]);    }if (argc > 3) {        printf("usage: selectechoclient <IPaddress> <Port>\n");return -1;    }

    connfd = socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons(servPort);    inet_pton(AF_INET, servInetAddr, &servaddr.sin_addr);

if (connect(connfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {        perror("connect error");return -1;    }    printf("welcome to selectechoclient\n");    handle(connfd);     /* do it all */    close(connfd);    printf("exit\n");    exit(0);}

void handle(int connfd){    FILE* fp = stdin;char sendline[MAXLINE], recvline[MAXLINE];    fd_set rset;    FD_ZERO(&rset);int maxfds = max(fileno(fp), connfd) + 1;int nread;for (;;) {        FD_SET(fileno(fp), &rset);        FD_SET(connfd, &rset);

if (select(maxfds, &rset, NULL, NULL, NULL) == -1) {            perror("select error");continue;        }

if (FD_ISSET(connfd, &rset)) {//接收到服务器响应            nread = read(connfd, recvline, MAXLINE);if (nread == 0) {                printf("server close the connection\n");break;            } else if (nread == -1) {                perror("read error");break;                }else {//server response                write(STDOUT_FILENO, recvline, nread);                }          }

if (FD_ISSET(fileno(fp), &rset)) {//标准输入可读            if (fgets(sendline, MAXLINE, fp) == NULL) {//eof exit                break;               } else {                write(connfd, sendline, strlen(sendline));              }        }

    } }

gcc selectechoserver.c -o selectechoserver

gcc selectechoclient.c -o selectechoclient