附录A：

#include #include #include #include #include #include #include #include #include #include #define PORT 3490 // the port client will be connecting to #define MAXDATASIZE 100 // max number of bytes we can get at once int main(int argc, char *argv[]) { int sockfd, numbytes; char buf[MAXDATASIZE]; struct hostent *he; struct sockaddr_in their_addr; // connector's address information security_context_t con = NULL; if (argc != 2) { fprintf(stderr,"usage: client hostname\n"); exit(1); } if ((he=gethostbyname(argv[1])) == NULL) { // get the host info herror("gethostbyname"); exit(1); } if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) { perror("socket"); exit(1); } their_addr.sin_family = AF_INET; // host byte order their_addr.sin_port = htons(PORT); // short, network byte order their_addr.sin_addr = *((struct in_addr *)he->h_addr); memset(&(their_addr.sin_zero), '\0', 8); // zero the rest of the struct if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) { perror("connect"); exit(1); } if ((numbytes=recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) { perror("recv"); exit(1); } if (getpeercon(sockfd, &con)) { perror("getpeercon"); } buf[numbytes] = '\0'; printf("Received: %s from %s\n",buf, con); close(sockfd); return 0; }

附录B：

#include #include #include #include #include #include #include #include #include #include #include #include #define MYPORT 3490 // the port users will be connecting to #define BACKLOG 10 // how many pending connections queue will hold void sigchld_handler(int s) { while(waitpid(-1, NULL, WNOHANG) > 0); } int main(void) { int sockfd, new_fd; // listen on sock_fd, new connection on new_fd struct sockaddr_in my_addr; // my address information struct sockaddr_in their_addr; // connector's address information socklen_t sin_size; struct sigaction sa; int yes=1; char buf[255]; socklen_t len=254; security_context_t con = NULL; if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) { perror("socket"); exit(1); } if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) { perror("setsockopt"); exit(1); } my_addr.sin_family = AF_INET; // host byte order my_addr.sin_port = htons(MYPORT); // short, network byte order my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP memset(&(my_addr.sin_zero), '\0', 8); // zero the rest of the struct if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) { perror("bind"); exit(1); } if (listen(sockfd, BACKLOG) == -1) { perror("listen"); exit(1); } sa.sa_handler = sigchld_handler; // reap all dead processes sigemptyset(&sa.sa_mask); sa.sa_flags = SA_RESTART; if (sigaction(SIGCHLD, &sa, NULL) == -1) { perror("sigaction"); exit(1); } while(1) { // main accept() loop sin_size = sizeof(struct sockaddr_in); if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1) { perror("accept"); continue; } // if (getsockopt(new_fd, SOL_SOCKET, SO_PEERSEC, con, &len)) { if (getpeercon(new_fd, &con)) { perror("getsockopt"); } printf("server: got connection from %s, %s\n", inet_ntoa(their_addr.sin_addr), con); if (!fork()) { // this is the child process close(sockfd); // child doesn't need the listener sprintf(buf, "Hello, %s", con); if (send(new_fd, buf, strlen(buf), 0) == -1) perror("send"); close(new_fd); exit(0); } close(new_fd); // parent doesn't need this } return 0; }

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