HP Rp7410 BSD Sockets Interface Programmer's Guide - Page 105
C L I E N T . U D P
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Using Internet Datagram Sockets Example Using Datagram Sockets sendto (s, &reqaddr, sizeof(struct in_addr), 0, &clientaddr_in, addrlen); } default: /* Parent process comes here. */ exit(0); } } /* * C L I E N T . U D P * * This is an example program that demonstrates the use of * datagram sockets as an BSD Sockets mechanism. This contains * the client, and is intended to operate in conjunction with the * server program found in serv.udp. Together, these two programs * demonstrate many of the features of sockets, as well as good * conventions for using these features. * * This program requests a service called "example". In order for * it to function, an entry for it needs to exist in the * /etc/services file. The port address for this service can be * any port number that is likely to be unused, such as 22375, * for example. The host on which the server will be runnin * must also have the same entry (same port number) in its * /etc/services file. * * The "example" service is an example of a simple name server * application. The host that is to provide this service is * required to be in the /etc/hosts file. Also, the host providing * this service presumably knows the internet addresses of many * hosts which the local host does not. Therefore, this program * will request the internet address of a target host by name from * the serving host. The serving host will return the requested * internet address as a response, and will return an address of * all ones if it does not recognize the host name. * */ #include #include #include #include #include #include #include extern int errno; int s; /* socket descriptor */ struct hostent *hp; struct servent *sp; /* pointer to info for nameserver host */ /* pointer to service information */ struct sockaddr_in myaddr_in; /* for local socket address */ struct sockaddr_in servaddr_in;/* for server socket addres */ Chapter 4 105