#include#include #include #include #include #include #include #include #include #define SERV_ADDR "127.0.0.1"#define SERV_PORT 5358#define BUF_LEN 1024#define MAX(a, b) (a)>(b)?(a):(b)ssize_t writen(int fd, const void *vptr, size_t n){ size_t nleft; ssize_t nwriten; const char *ptr; ptr = vptr; nleft = n; while(nleft>0) { if((nwriten = write(fd, ptr, nleft)) <= 0) { if(nwriten < 0 && errno == EINTR) { nwriten = 0; /*interrupt by signal*/ } else { return -1; } } nleft -= nwriten; ptr += nwriten; } return n;}void str_cli(FILE *fp, int sockfd){ int maxfdp, n; int stdineof = 0; fd_set rset; char sendbuf[BUF_LEN] = { 0}; char recvbuf[BUF_LEN] = { 0}; FD_ZERO(&rset); while(1) { FD_SET(fileno(fp), &rset); FD_SET(sockfd, &rset); maxfdp = MAX(fileno(fp), sockfd) + 1; select(maxfdp, &rset, NULL, NULL, NULL); if(FD_ISSET(sockfd, &rset)) { if(read(sockfd, recvbuf, BUF_LEN) == 0) { //if the length of the data in kernal buffer > 1024 ? if(stdineof == 1) { shutdown(sockfd, SHUT_RD); return; } else { printf("err_quit\n"); close(sockfd); return; } } else { fputs(recvbuf, stdout); } } if(FD_ISSET(fileno(fp), &rset)) { if((n = read(fileno(fp), sendbuf, BUF_LEN)) == 0) { stdineof = 1; shutdown(sockfd, SHUT_WR); FD_CLR(fileno(fp), &rset); continue; } writen(sockfd, sendbuf, strlen(sendbuf)); } bzero(sendbuf, BUF_LEN); bzero(recvbuf, BUF_LEN); } return;}int main(int argc, char **argv){ int fd; struct sockaddr_in servaddr; fd = socket(AF_INET, SOCK_STREAM, 0); bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = inet_addr(SERV_ADDR); servaddr.sin_port = htons(SERV_PORT); if (connect(fd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) { printf("connect error: %s\n", strerror(errno)); return 0; } str_cli(stdin, fd); return 0;}
改进之处:
1、采用系统调用进行I/O而不是I/O库函数，防止了I/O缓冲导致的问题。
2、采用shutdown函数代替close函数，防止client端在未收到所有的返回数据前关闭。
close与shutdown的区别:
1、close函数把描述字的引用计数减1，只有在引用计数为0时才关闭描述字。
shutdown不管引用计数，直接激发TCP发送FIN终止正常连接。
2、close终止传输的两个方向(读/写)，shutdown则可以选择关闭读/写/读写。