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nicolgonicolgo
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add sample code of beej's guide of networking programming
1 parent 7a298c5 commit a325c1c

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‎bgnet_examples/Makefile

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TARGETS=broadcaster client getip ghbn ieee754 listener pack pack2 \
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poll pollserver select selectserver server showip talker telnot
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CC=gcc
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CCOPTS=-Wall -Wextra
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.PHONY: all clean pristine
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all: $(TARGETS)
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clean:
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rm -f $(TARGETS)
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pristine: clean
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%: %.c
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$(CC) $(CCOPTS) -o $@ $<

‎bgnet_examples/README.md

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# Beej's Guide to Network Programming Examples
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Type `make` to build.
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‎bgnet_examples/broadcaster.c

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/*
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** broadcaster.c -- a datagram "client" like talker.c, except
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** this one can broadcast
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <netdb.h>
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#define SERVERPORT 4950 // the port users will be connecting to
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int main(int argc, char *argv[])
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{
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int sockfd;
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struct sockaddr_in their_addr; // connector's address information
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struct hostent *he;
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int numbytes;
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int broadcast = 1;
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//char broadcast = '1'; // if that doesn't work, try this
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if (argc != 3) {
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fprintf(stderr,"usage: broadcaster hostname message\n");
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exit(1);
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}
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if ((he=gethostbyname(argv[1])) == NULL) { // get the host info
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perror("gethostbyname");
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exit(1);
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}
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if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
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perror("socket");
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exit(1);
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}
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// this call is what allows broadcast packets to be sent:
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if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
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sizeof broadcast) == -1) {
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perror("setsockopt (SO_BROADCAST)");
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exit(1);
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}
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their_addr.sin_family = AF_INET; // host byte order
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their_addr.sin_port = htons(SERVERPORT); // short, network byte order
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their_addr.sin_addr = *((struct in_addr *)he->h_addr);
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memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero);
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if ((numbytes=sendto(sockfd, argv[2], strlen(argv[2]), 0,
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(struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
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perror("sendto");
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exit(1);
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}
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printf("sent %d bytes to %s\n", numbytes,
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inet_ntoa(their_addr.sin_addr));
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close(sockfd);
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return 0;
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}

‎bgnet_examples/client.c

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/*
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** client.c -- a stream socket client demo
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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#include <netdb.h>
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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#define PORT "3490" // the port client will be connecting to
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#define MAXDATASIZE 100 // max number of bytes we can get at once
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// get sockaddr, IPv4 or IPv6:
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void *get_in_addr(struct sockaddr *sa)
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{
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if (sa->sa_family == AF_INET) {
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return &(((struct sockaddr_in*)sa)->sin_addr);
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}
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return &(((struct sockaddr_in6*)sa)->sin6_addr);
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}
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int main(int argc, char *argv[])
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{
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int sockfd, numbytes;
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char buf[MAXDATASIZE];
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struct addrinfo hints, *servinfo, *p;
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int rv;
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char s[INET6_ADDRSTRLEN];
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if (argc != 2) {
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fprintf(stderr,"usage: client hostname\n");
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exit(1);
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}
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memset(&hints, 0, sizeof hints);
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) {
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fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
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return 1;
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}
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// loop through all the results and connect to the first we can
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for(p = servinfo; p != NULL; p = p->ai_next) {
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if ((sockfd = socket(p->ai_family, p->ai_socktype,
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p->ai_protocol)) == -1) {
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perror("client: socket");
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continue;
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}
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if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
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perror("client: connect");
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close(sockfd);
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continue;
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}
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break;
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}
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if (p == NULL) {
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fprintf(stderr, "client: failed to connect\n");
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return 2;
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}
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inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
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s, sizeof s);
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printf("client: connecting to %s\n", s);
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freeaddrinfo(servinfo); // all done with this structure
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if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
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perror("recv");
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exit(1);
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}
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buf[numbytes] = '\0';
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printf("client: received '%s'\n",buf);
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close(sockfd);
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return 0;
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}
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‎bgnet_examples/getip.c

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/*
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** getip.c -- a hostname lookup demo
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <netdb.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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int main(int argc, char *argv[])
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{
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struct hostent *h;
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if (argc != 2) { // error check the command line
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fprintf(stderr,"usage: getip address\n");
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exit(1);
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}
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if ((h=gethostbyname(argv[1])) == NULL) { // get the host info
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herror("gethostbyname");
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exit(1);
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}
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printf("Host name : %s\n", h->h_name);
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printf("IP Address : %s\n", inet_ntoa(*((struct in_addr *)h->h_addr)));
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return 0;
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}

‎bgnet_examples/ghbn.c

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/*
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** ghbn.c -- a hostname lookup demo
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**
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** THIS IS A DEPRECATED METHOD OF GETTING HOST NAMES
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** use getaddrinfo() instead.
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*/
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#include <stdio.h>
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#include <errno.h>
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#include <netdb.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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int main(int argc, char *argv[])
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{
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int i;
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struct hostent *he;
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struct in_addr **addr_list;
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if (argc != 2) { // error check the command line
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fprintf(stderr,"usage: ghbn hostname\n");
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return 1;
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}
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if ((he = gethostbyname(argv[1])) == NULL) { // get the host info
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herror("gethostbyname");
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return 2;
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}
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// print information about this host:
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printf("Official name is: %s\n", he->h_name);
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printf(" IP addresses: ");
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addr_list = (struct in_addr **)he->h_addr_list;
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for(i = 0; addr_list[i] != NULL; i++) {
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printf("%s ", inet_ntoa(*addr_list[i]));
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}
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printf("\n");
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return 0;
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}

‎bgnet_examples/ieee754.c

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#include <stdio.h>
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#include <stdint.h>
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#include <inttypes.h>
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#define pack754_32(f) (pack754((f), 32, 8))
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#define pack754_64(f) (pack754((f), 64, 11))
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#define unpack754_32(i) (unpack754((i), 32, 8))
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#define unpack754_64(i) (unpack754((i), 64, 11))
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uint64_t pack754(long double f, unsigned bits, unsigned expbits)
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{
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long double fnorm;
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int shift;
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long long sign, exp, significand;
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unsigned significandbits = bits - expbits - 1; // -1 for sign bit
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if (f == 0.0) return 0; // get this special case out of the way
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// check sign and begin normalization
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if (f < 0) { sign = 1; fnorm = -f; }
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else { sign = 0; fnorm = f; }
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// get the normalized form of f and track the exponent
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shift = 0;
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while(fnorm >= 2.0) { fnorm /= 2.0; shift++; }
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while(fnorm < 1.0) { fnorm *= 2.0; shift--; }
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fnorm = fnorm - 1.0;
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// calculate the binary form (non-float) of the significand data
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significand = fnorm * ((1LL<<significandbits) + 0.5f);
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// get the biased exponent
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exp = shift + ((1<<(expbits-1)) - 1); // shift + bias
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// return the final answer
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return (sign<<(bits-1)) | (exp<<(bits-expbits-1)) | significand;
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}
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long double unpack754(uint64_t i, unsigned bits, unsigned expbits)
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{
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long double result;
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long long shift;
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unsigned bias;
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unsigned significandbits = bits - expbits - 1; // -1 for sign bit
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if (i == 0) return 0.0;
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// pull the significand
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result = (i&((1LL<<significandbits)-1)); // mask
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result /= (1LL<<significandbits); // convert back to float
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result += 1.0f; // add the one back on
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// deal with the exponent
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bias = (1<<(expbits-1)) - 1;
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shift = ((i>>significandbits)&((1LL<<expbits)-1)) - bias;
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while(shift > 0) { result *= 2.0; shift--; }
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while(shift < 0) { result /= 2.0; shift++; }
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// sign it
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result *= (i>>(bits-1))&1? -1.0: 1.0;
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return result;
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}
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int main(void)
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{
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float f = 3.1415926, f2;
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double d = 3.14159265358979323, d2;
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uint32_t fi;
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uint64_t di;
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fi = pack754_32(f);
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f2 = unpack754_32(fi);
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di = pack754_64(d);
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d2 = unpack754_64(di);
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printf("float before : %.7f\n", f);
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printf("float encoded: 0x%08" PRIx32 "\n", fi);
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printf("float after : %.7f\n\n", f2);
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printf("double before : %.20lf\n", d);
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printf("double encoded: 0x%016" PRIx64 "\n", di);
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printf("double after : %.20lf\n", d2);
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return 0;
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}
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