books: boooks examples, Beejs Guide ex-s

books/bgnet_examples/Makefile

@@ -0,0 +1,17 @@
+TARGETS=broadcaster client getip ghbn ieee754 listener pack pack2 \
+	poll pollserver select selectserver server showip talker telnot
+
+CC=gcc
+CCOPTS=-Wall -Wextra
+
+.PHONY: all clean pristine
+
+all: $(TARGETS)
+
+clean:
+	rm -f $(TARGETS)
+
+pristine: clean
+
+%: %.c
+	$(CC) $(CCOPTS) -o $@ $<

books/bgnet_examples/README.md

@@ -0,0 +1,4 @@
+# Beej's Guide to Network Programming Examples
+
+Type `make` to build.
+

books/bgnet_examples/broadcaster.c

@@ -0,0 +1,67 @@
+/*
+** broadcaster.c -- a datagram "client" like talker.c, except
+**                  this one can broadcast
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+
+#define SERVERPORT 4950	// the port users will be connecting to
+
+int main(int argc, char *argv[])
+{
+	int sockfd;
+	struct sockaddr_in their_addr; // connector's address information
+	struct hostent *he;
+	int numbytes;
+	int broadcast = 1;
+	//char broadcast = '1'; // if that doesn't work, try this
+
+	if (argc != 3) {
+		fprintf(stderr,"usage: broadcaster hostname message\n");
+		exit(1);
+	}
+
+	if ((he=gethostbyname(argv[1])) == NULL) {  // get the host info
+		perror("gethostbyname");
+		exit(1);
+	}
+
+	if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
+		perror("socket");
+		exit(1);
+	}
+
+	// this call is what allows broadcast packets to be sent:
+	if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
+		sizeof broadcast) == -1) {
+		perror("setsockopt (SO_BROADCAST)");
+		exit(1);
+	}
+
+	their_addr.sin_family = AF_INET;	 // host byte order
+	their_addr.sin_port = htons(SERVERPORT); // short, network byte order
+	their_addr.sin_addr = *((struct in_addr *)he->h_addr);
+	memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero);
+
+	if ((numbytes=sendto(sockfd, argv[2], strlen(argv[2]), 0,
+			 (struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
+		perror("sendto");
+		exit(1);
+	}
+
+	printf("sent %d bytes to %s\n", numbytes,
+		inet_ntoa(their_addr.sin_addr));
+
+	close(sockfd);
+
+	return 0;
+}

books/bgnet_examples/client.c

@@ -0,0 +1,94 @@
+/*
+** client.c -- a stream socket client demo
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <netdb.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+
+#include <arpa/inet.h>
+
+#define PORT "3490" // the port client will be connecting to 
+
+#define MAXDATASIZE 100 // max number of bytes we can get at once 
+
+// get sockaddr, IPv4 or IPv6:
+void *get_in_addr(struct sockaddr *sa)
+{
+	if (sa->sa_family == AF_INET) {
+		return &(((struct sockaddr_in*)sa)->sin_addr);
+	}
+
+	return &(((struct sockaddr_in6*)sa)->sin6_addr);
+}
+
+int main(int argc, char *argv[])
+{
+	int sockfd, numbytes;  
+	char buf[MAXDATASIZE];
+	struct addrinfo hints, *servinfo, *p;
+	int rv;
+	char s[INET6_ADDRSTRLEN];
+
+	if (argc != 2) {
+	    fprintf(stderr,"usage: client hostname\n");
+	    exit(1);
+	}
+
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+
+	if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) {
+		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
+		return 1;
+	}
+
+	// loop through all the results and connect to the first we can
+	for(p = servinfo; p != NULL; p = p->ai_next) {
+		if ((sockfd = socket(p->ai_family, p->ai_socktype,
+				p->ai_protocol)) == -1) {
+			perror("client: socket");
+			continue;
+		}
+
+		if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
+			perror("client: connect");
+			close(sockfd);
+			continue;
+		}
+
+		break;
+	}
+
+	if (p == NULL) {
+		fprintf(stderr, "client: failed to connect\n");
+		return 2;
+	}
+
+	inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
+			s, sizeof s);
+	printf("client: connecting to %s\n", s);
+
+	freeaddrinfo(servinfo); // all done with this structure
+
+	if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
+	    perror("recv");
+	    exit(1);
+	}
+
+	buf[numbytes] = '\0';
+
+	printf("client: received '%s'\n",buf);
+
+	close(sockfd);
+
+	return 0;
+}
+

books/bgnet_examples/getip.c

@@ -0,0 +1,32 @@
+/*
+** getip.c -- a hostname lookup demo
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <netdb.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+int main(int argc, char *argv[])
+{
+	struct hostent *h;
+
+	if (argc != 2) {  // error check the command line
+		fprintf(stderr,"usage: getip address\n");
+		exit(1);
+	}
+
+	if ((h=gethostbyname(argv[1])) == NULL) {  // get the host info
+		herror("gethostbyname");
+		exit(1);
+	}
+
+	printf("Host name  : %s\n", h->h_name);
+	printf("IP Address : %s\n", inet_ntoa(*((struct in_addr *)h->h_addr)));
+
+   return 0;
+}

books/bgnet_examples/ghbn.c

@@ -0,0 +1,42 @@
+/*
+** ghbn.c -- a hostname lookup demo
+**
+** THIS IS A DEPRECATED METHOD OF GETTING HOST NAMES
+** use getaddrinfo() instead.
+*/
+
+#include <stdio.h>
+#include <errno.h>
+#include <netdb.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+int main(int argc, char *argv[])
+{
+	int i;
+	struct hostent *he;
+	struct in_addr **addr_list;
+
+	if (argc != 2) {  // error check the command line
+		fprintf(stderr,"usage: ghbn hostname\n");
+		return 1;
+	}
+
+	if ((he = gethostbyname(argv[1])) == NULL) {  // get the host info
+		herror("gethostbyname");
+		return 2;
+	}
+
+	// print information about this host:
+	printf("Official name is: %s\n", he->h_name);
+	printf("    IP addresses: ");
+	addr_list = (struct in_addr **)he->h_addr_list;
+	for(i = 0; addr_list[i] != NULL; i++) {
+		printf("%s ", inet_ntoa(*addr_list[i]));
+	}
+	printf("\n");
+
+	return 0;
+}

books/bgnet_examples/ieee754.c

@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#define pack754_32(f) (pack754((f), 32, 8))
+#define pack754_64(f) (pack754((f), 64, 11))
+#define unpack754_32(i) (unpack754((i), 32, 8))
+#define unpack754_64(i) (unpack754((i), 64, 11))
+
+uint64_t pack754(long double f, unsigned bits, unsigned expbits)
+{
+	long double fnorm;
+	int shift;
+	long long sign, exp, significand;
+	unsigned significandbits = bits - expbits - 1; // -1 for sign bit
+
+	if (f == 0.0) return 0; // get this special case out of the way
+
+	// check sign and begin normalization
+	if (f < 0) { sign = 1; fnorm = -f; }
+	else { sign = 0; fnorm = f; }
+
+	// get the normalized form of f and track the exponent
+	shift = 0;
+	while(fnorm >= 2.0) { fnorm /= 2.0; shift++; }
+	while(fnorm < 1.0) { fnorm *= 2.0; shift--; }
+	fnorm = fnorm - 1.0;
+
+	// calculate the binary form (non-float) of the significand data
+	significand = fnorm * ((1LL<<significandbits) + 0.5f);
+
+	// get the biased exponent
+	exp = shift + ((1<<(expbits-1)) - 1); // shift + bias
+
+	// return the final answer
+	return (sign<<(bits-1)) | (exp<<(bits-expbits-1)) | significand;
+}
+
+long double unpack754(uint64_t i, unsigned bits, unsigned expbits)
+{
+	long double result;
+	long long shift;
+	unsigned bias;
+	unsigned significandbits = bits - expbits - 1; // -1 for sign bit
+
+	if (i == 0) return 0.0;
+
+	// pull the significand
+	result = (i&((1LL<<significandbits)-1)); // mask
+	result /= (1LL<<significandbits); // convert back to float
+	result += 1.0f; // add the one back on
+
+	// deal with the exponent
+	bias = (1<<(expbits-1)) - 1;
+	shift = ((i>>significandbits)&((1LL<<expbits)-1)) - bias;
+	while(shift > 0) { result *= 2.0; shift--; }
+	while(shift < 0) { result /= 2.0; shift++; }
+
+	// sign it
+	result *= (i>>(bits-1))&1? -1.0: 1.0;
+
+	return result;
+}
+
+int main(void)
+{
+	float f = 3.1415926, f2;
+	double d = 3.14159265358979323, d2;
+	uint32_t fi;
+	uint64_t di;
+
+	fi = pack754_32(f);
+	f2 = unpack754_32(fi);
+
+	di = pack754_64(d);
+	d2 = unpack754_64(di);
+
+	printf("float before : %.7f\n", f);
+	printf("float encoded: 0x%08" PRIx32 "\n", fi);
+	printf("float after  : %.7f\n\n", f2);
+
+	printf("double before : %.20lf\n", d);
+	printf("double encoded: 0x%016" PRIx64 "\n", di);
+	printf("double after  : %.20lf\n", d2);
+
+	return 0;
+}
+