| 24.1 | Yes, in the first example, 2 bytes are sent with a single urgent pointer that points to the byte following the b . But in the second example (the two function calls), first the a is sent with an urgent pointer that points just beyond it, and this is followed by another TCP segment containing the b with a different urgent pointer that points just beyond it. |
| 24.2 | 24.2 Figure E.16 shows the version using poll . Figure E.16 Version of Figure 24.6 using poll instead of select . oob/tcprecv03p.c 1 #include "unp.h" 2 int 3 main(int argc, char **argv) 4 { 5 int listenfd, connfd, n, justreadoob = 0; 6 char buff[100]; 7 struct pollfd pollfd[1]; 8 if (argc == 2) 9 listenfd = Tcp_listen(NULL, argv[1], NULL); 10 else if (argc == 3) 11 listenfd = Tcp_listen(argv[1], argv[2], NULL); 12 else 13 err_quit("usage: tcprecv03p [ <host> ] <port#>"); 14 connfd = Accept(listenfd, NULL, NULL); 15 pollfd[0].fd = connfd; 16 pollfd[0].events = POLLRDNORM; 17 for ( ; ; ) { 18 if (justreadoob == 0) 19 pollfd[0].events= POLLRDBAND; 20 Poll(pollfd, 1, INFTIM); 21 if (pollfd[0].revents & POLLRDBAND) { 22 n = Recv(connfd, buff, sizeof(buff) - 1, MSG_OOB); 23 buff[n] = 0; /* null terminate */ 24 printf("read %d OOB byte: %s\n", n, buff); 25 justreadoob = 1; 26 pollfd[0].events &= ~POLLRDBAND; /* turn bit off */ 27 } 28 if (pollfd[0].revents & POLLRDNORM) { 29 if ( (n = Read(connfd, buff, sizeof(buff) - 1)) == 0) { 30 printf("received EOF\n"); 31 exit(0); 32 } 33 buff[n] = 0; /* null terminate */ 34 printf("read %d bytes: %s\n", n, buff); 35 justreadoob = 0; 36 } 37 } 38 } |
