标签：set out struct const 利用 循环 直接 pid_t 套接口
recv相对于read有什么区别呢？
其实它跟read函数功能一样，都可以从套接口缓冲区sockfd中取数据到buf,但是recv仅仅只能够用于套接口IO，并不能用于文件IO以及其它的IO，而read函数可以用于任何的IO；
recv函数相比read函数多了一个flags参数，通过这个参数可以指定接收的行为，比较有用的两个选项是：
这个这次要学习的，它可以接收缓冲区中的数据，但是并不从缓冲区中清除，这是跟read函数有区别的地方，read函数一旦读取了，就会直接从缓冲区中清除。
readline实现
也就是实现按行读取，读取直到\n字符，实际上，它也能解决上节中提到的粘包问题，回顾下上节的粘包问题解决方案：
包尾加\r\n(ftp)
我们只要解释\n为止，表示前面是一个条合法的消息，对于readline的实现，可以有三种方案：
①、最简单的方案就是一个字符一个字符的读取，然后做判断是否有"\n"，但是这种效率比较低，因为会多次掉用read或recv系统函数。
②、用一个static变量保存接收到的数据进行缓存，在下次时从这个缓存变量中读取然后估"\n"判断。但是一旦用到了static变量，这意味着用到的函数是不可重录函数【关于这个概念，可以参考博文：http://www.cnblogs.com/webor2006/p/3744002.html】。
③、偷窥的方法，也就是这次要采用的方案。下面就利用我们封装的recv_peek函数实现readline：
server.c
#include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <errno.h> #define ERR_EXIT(m) do { perror(m); exit(EXIT_FAILURE); }while(0); ssize_t readn(int fd, void *buf, size_t count)//读取count个字节数，其中size_t是无符号 的整数，ssize_t是有符号的整数 { size_t nleft = count;//剩余的字节数 printf("nleft = %d\n",nleft); ssize_t nread;//已接收的字节数 char *bufp = (char*)buf; while (nleft > 0) {//由于不能保证一次读操作能够返回字节数是多少，所以需要进行循环来接收 if ((nread = read(fd, bufp, nleft)) < 0) { if (errno == EINTR)//被信号中断了，则继续执行，因为不是出错 continue; return -1;//表示读取失败了 } else if (nread == 0)//对等方关闭了 return count - nleft;//返回已经读取的字节数 bufp += nread; nleft -= nread; } return count; } ssize_t writen(int fd, const void *buf, size_t count) { size_t nleft = count; ssize_t nwritten; char *bufp = (char*)buf; while (nleft > 0) { if ((nwritten = write(fd, bufp, nleft)) < 0) { if (errno == EINTR) continue; return -1; } else if (nwritten == 0)//如果是这种情况，则表示什么都没发生，继续还得执行 continue; bufp += nwritten; nleft -= nwritten; } 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 = buf; int nleft = maxline; while(1) { ret = recv_peek(sockfd,bufp,nleft); if(ret < 0) return ret; else if(ret == 0) return ret; nread = ret; int i; for(i = 0; i<nread; i++) { if(bufp[i] == ‘\n‘) { ret = readn(sockfd,bufp,i+1); if(ret != i+1) exit(EXIT_FAILURE); return ret; } } if(nread > nleft) exit(EXIT_FAILURE); nleft -= nread; ret = readn(sockfd,bufp,nread); if(ret != nread) exit(EXIT_FAILURE); bufp += nread; } return -1; } void do_service(int conn) { char recvbuf[1024]; //struct packet recvbuf; int n; while(1) { memset(recvbuf, 0, sizeof(recvbuf)); int ret=readline(conn,recvbuf,1024); if(ret == -1) { ERR_EXIT("readline"); } if(ret == 0) { printf("client close\n"); break; } fputs(recvbuf,stdout); writen(conn,recvbuf,strlen(recvbuf)); } } int main(void) { int listenfd; if((listenfd = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) < 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); /*servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");*/ /*inet_aton("127.0.0.1",&servaddr.sin_addr);*/ //地址重用 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("listen"); } struct sockaddr_in peeraddr; socklen_t peerlen = sizeof(peeraddr); int confd; pid_t pid; while(1) { if((confd = 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 = fork(); if(pid == -1) { ERR_EXIT("fork"); } if(pid == 0) { close(listenfd); do_service(confd); exit(EXIT_SUCCESS); } else { close(confd); } } return 0; }
client.c
#include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <errno.h> #define ERR_EXIT(m) do { perror(m); exit(EXIT_FAILURE); }while(0); ssize_t readn(int fd, void *buf, size_t count)//需要将函数的定义也挪过来 { 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 += nread; nleft -= nread; } return count; } ssize_t writen(int fd, const void *buf, size_t count) { size_t nleft = count; ssize_t nwritten; char *bufp = (char*)buf; while (nleft > 0) { if ((nwritten = write(fd, bufp, nleft)) < 0) { if (errno == EINTR) continue; return -1; } else if (nwritten == 0) continue; bufp += nwritten; nleft -= nwritten; } 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 = buf; int nleft = maxline; while(1) { ret = recv_peek(sockfd,bufp,nleft); if(ret < 0) return ret; else if(ret == 0) return ret; nread = ret; int i; for(i = 0; i < nread; i++) { if(bufp[i] == ‘\n‘) { ret = readn(sockfd,bufp,i+1); if(ret != i+1) exit(EXIT_FAILURE); return ret; } } if(nread > nleft) exit(EXIT_FAILURE); nleft -= nread; ret = readn(sockfd,bufp,nread); if(ret != nread) exit(EXIT_FAILURE); bufp += nread; } return -1; } int main(void) { int sockfd; if((sockfd = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) < 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("127.0.0.1"); /*inet_aton("127.0.0.1",&servaddr.sin_addr);*/ if (connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr)) < 0) { ERR_EXIT("connect"); } struct sockaddr_in localaddr; socklen_t addrlen = sizeof(localaddr); if(getsockname(sockfd,(struct sockaddr*)&localaddr,&addrlen) < 0) ERR_EXIT("getsockname"); printf("ip = %s, port = %d\n",inet_ntoa(localaddr.sin_addr),ntohs(localaddr.s in_port)); char sendbuf[1024] = {0}; char recvbuf[1024] = {0}; //struct packet sendbuf; //struct packet recvbuf; //memset(&sendbuf,0,sizeof(sendbuf)); //memset(&recvbuf,0,sizeof(recvbuf)); int n; while(fgets(sendbuf,sizeof(sendbuf),stdin) != NULL) { //writen(sockfd,sendbuf,sizeof(sendbuf)); //readn(sockfd,recvbuf,sizeof(recvbuf)); //n =strlen(sendbuf.buf); //sendbuf.len = htonl(n);//网络字节序 writen(sockfd,sendbuf,strlen(sendbuf)); int ret = readline(sockfd,recvbuf,sizeof(recvbuf)); //int ret = readn(sockfd,&recvbuf.len,4); if(ret == -1) { ERR_EXIT("read"); } else if(ret == 0) { printf("client close\n"); break; } fputs(recvbuf,stdout); memset(sendbuf,0,sizeof(sendbuf)); memset(recvbuf,0,sizeof(recvbuf)); } close(sockfd); return 0; }
Makefile
.PHONY: clean all CC=gcc CFLAGE= -G -Wall BIN=client server getiplist all:$(BIN) %.o:%.c $(CC) $(cflags) -C $< -O $@ clean: rm -f *.o $(BIN)
getsockname:获取套接口本地的地址
当客户端成功与服务端连接之后，如果想知道客户端的地址，就可以通过它来获取，
getpeername:获取对等方的地址
由于它的使用方法跟getsockname一样，这里就不说明了，注意：sockfd需是连接成功的套接口，另外对于服务端获取客户端ip，像这种情况下也需用这个接口来获得：
gethostname:获取主机的名称
gethostbyname:通过主机名来获取主机上所有的ip地址
#include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.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) int getlocalip(char *ip) { char host[100] = {0}; if (gethostname(host, sizeof(host)) < 0) return -1; struct hostent *hp; if ((hp = gethostbyname(host)) == NULL) return -1; strcpy(ip, inet_ntoa(*(struct in_addr*)hp->h_addr_list[0])); return 0; } int main(void) { char host[100] = {0}; if (gethostname(host, sizeof(host)) < 0) ERR_EXIT("gethostname"); struct hostent *hp; if ((hp = gethostbyname(host)) == NULL) ERR_EXIT("gethostbyname"); int i = 0; while (hp->h_addr_list[i] != NULL) { printf("%s\n", inet_ntoa(*(struct in_addr*)hp->h_addr_list[i])); i++; } char ip[16] = {0}; getlocalip(ip); printf("localip=%s\n", ip); return 0; }
read、write 与recv、send区别 gethostname
标签：set out struct const 利用 循环 直接 pid_t 套接口
原文地址：https://www.cnblogs.com/Malphite/p/11645067.html
