I have a scenario like the client has to search for the active server.There will be many servers.But not all server are active.And at a time not more than one server will be active.

The client will be in active state always i.e, it should always search for an active server until it gets one.I have all the servers' ip address in a file.what i thought is like creating a loop that will try to connect with all ip address in the file.if any of the ip address is active it can connect with that server and get the information from a file in the server.It was working properly sometimes and sometimes it displays blank.I think there is some memory problem with the variable "buff".Can someone help me out in this??

i checked with the server program.Its working properly.I think the poblem is with the client program only.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/wait.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#define MAX 100
#define IPSIZE 20

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);

char buff[100];
char buf[100];
char *cont;

int main()
    int sockfd, new_fd, numbytes;
    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_storage their_addr;
    int yes = 1, len = 16, i = 0;
    char names[20];
    char line[75];
    char opr[2];
    char s[INET6_ADDRSTRLEN];
    char **lines_array;
    int rv, line_counter = 0;;
    FILE *fp;
    struct sockaddr *name;
    socklen_t size;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    fp = fopen("ipadd.ini", "r");
    while (fgets(line, sizeof(line), fp) != NULL) {
    lines_array = (char **) malloc((line_counter) * IPSIZE);
    if (fp == NULL) {
	printf("cannot open file");
	return 1;
    } else {
	while (fgets(line, sizeof(line), fp) != NULL) {
	    lines_array[i++] = strdup(line);
    printf("Line counter %d", line_counter);
    /* for (i = 0; i <line_counter; i++) 
       printf("\n%s", lines_array[i]);

       free(lines_array); */
    int su = 0;

    while (su == 0) {
	i = 0;

	while (i < line_counter) {
	    if ((rv =
		 getaddrinfo(lines_array[i], "3456", &hints,
			     &servinfo)) == -1) {
		fprintf(stderr, "getaddrinfo:%s", gai_strerror(rv));

	    for (p = servinfo; p != NULL; p = p->ai_next) {

		if ((sockfd =
		     socket(p->ai_family, p->ai_socktype,
			    p->ai_protocol)) == -1) {
		    perror("\n client:socket");
		printf(" socket %d\n", sockfd);

		if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {


	    if (p == NULL) {
		fprintf(stderr, "client:failed");

	    strcpy(names, lines_array[i++]);

		      get_in_addr((struct sockaddr *) p->ai_addr), s,
		      sizeof s);
	    int count = 2;
	    if (recv(sockfd, buf, sizeof buf, 0) == -1)
	    len = 0;

	    printf("message from server:%s", buf);

	    if ((send(sockfd, names, sizeof names, 0)) == -1)

	    if ((recv(sockfd, buf, sizeof buf, 0)) == -1)
	    printf("\n The no of lines in file is %s", buf); 
	    len = count = atoi(buf);
	    printf("\ncount %d", count);//till this it works good
	    while (count != 0) {
		if ((recv(sockfd, buff, sizeof buff, 0)) == -1)
		printf("\n%s", buff);// Here is the problem:prints blank
		count--;       //The server sends the information         
                               //successfully but the client receives it  
                               //correctly sometimes,but not always. 

	    if (len > 0)
		return 2;
	i = 0;


    return 0;

line 56: initialize variable i to 0.

line 75: fgets() adds the '\n' to the end of each line when '\n' appears in the data file. I don't know off-hand it that will cause problems for getaddrinfo() or not. You might add code between lines 57 and 58 to strip off '\n', and see if that fixed your problem.

As for buff -- I don't see how that could be the problem.

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