1 .\" Copyright (c) 1986, 1993 2 .\" The Regents of the University of California. All rights reserved. 3 .\" 4 .\" Redistribution and use in source and binary forms, with or without 5 .\" modification, are permitted provided that the following conditions 6 .\" are met: 7 .\" 1. Redistributions of source code must retain the above copyright 8 .\" notice, this list of conditions and the following disclaimer. 9 .\" 2. Redistributions in binary form must reproduce the above copyright 10 .\" notice, this list of conditions and the following disclaimer in the 11 .\" documentation and/or other materials provided with the distribution. 12 .\" 3. Neither the name of the University nor the names of its contributors 13 .\" may be used to endorse or promote products derived from this software 14 .\" without specific prior written permission. 15 .\" 16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 .\" SUCH DAMAGE. 27 .\" 28 #include <sys/types.h> 29 #include <sys/socket.h> 30 #include <netinet/in.h> 31 #include <stdio.h> 32 33 /* 34 * In the included file <netinet/in.h> a sockaddr_in is defined as follows: 35 * struct sockaddr_in { 36 * short sin_family; 37 * u_short sin_port; 38 * struct in_addr sin_addr; 39 * char sin_zero[8]; 40 * }; 41 * 42 * This program creates a datagram socket, binds a name to it, then reads 43 * from the socket. 44 */ 45 main() 46 { 47 int sock, length; 48 struct sockaddr_in name; 49 char buf[1024]; 50 51 /* Create socket from which to read. */ 52 sock = socket(AF_INET, SOCK_DGRAM, 0); 53 if (sock < 0) { 54 perror("opening datagram socket"); 55 exit(1); 56 } 57 /* Create name with wildcards. */ 58 name.sin_family = AF_INET; 59 name.sin_addr.s_addr = INADDR_ANY; 60 name.sin_port = 0; 61 if (bind(sock, &name, sizeof(name))) { 62 perror("binding datagram socket"); 63 exit(1); 64 } 65 /* Find assigned port value and print it out. */ 66 length = sizeof(name); 67 if (getsockname(sock, &name, &length)) { 68 perror("getting socket name"); 69 exit(1); 70 } 71 printf("Socket has port #%d\en", ntohs(name.sin_port)); 72 /* Read from the socket */ 73 if (read(sock, buf, 1024) < 0) 74 perror("receiving datagram packet"); 75 printf("-->%s\en", buf); 76 close(sock); 77 } 78