client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

struct servent * getService(char *, char *);
struct hostent * getHost(char *);

int getSocket(int, int, int);

int main(int argc, char *argv[]) {
	struct servent *servinfo;
	struct hostent *servhost;
	char *port = "ftp";
	char *host_name;
	struct sockaddr_in server;
	int sock;
	
	// プログラムの引数をhostname,サービス名とする
	if (sizeof(argv) < 2) {
		printf("rterm host_name {service_name}");
		exit(0);
	}
	host_name = argv[1];
	printf("gethostname: OK\n");
	if (argv[2] != NULL) {
		port = argv[2];
	}

	servinfo = getService(port, "tcp");
	servhost = getHost(host_name);
	
	sock = getSocket(AF_INET, SOCK_STREAM, 0);
	
	memset((char *)&server, 0, sizeof(server));
	server.sin_family = AF_INET;
	server.sin_port = htons(servinfo->s_port);
	memcpy((char *)&server.sin_addr, servhost->h_addr, servhost->h_length);
	if (connect(sock, (struct sockaddr *)&server, sizeof(server)) == -1) {
		perror("connect");
		exit(0);
	}
	printf("connect: OK");
	
	return 0;
}

struct servent * getService(char *port, char *proto) {
	struct servent *a;
	
	a = getservbyname(port, proto);
	if (a == NULL) {
		perror("getservbyname");
		exit(0);
	}
	printf("getservbyname: OK\n");
	
	return a;
}

struct hostent * getHost(char *host_name) {
	struct hostent *a;
	unsigned long addr;
	
	a = gethostbyname(host_name);
	if (a == NULL) {
		addr = inet_addr(host_name);
		a = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET);
		if (a == NULL) {
			perror("gethostbyaddr");
			exit(0);
		}
	}
	printf("gethostname: OK\n");
	
	return a;
}

int getSocket(int domain, int type, int proto) {
	int a;
	
	a = socket(domain, type, proto);
	if (a < 0) {
		perror("socket");
		exit(0);
	}
	printf("socket: OK\n");
	
	return a;

}