TCP server not waiting for client response? - c

Question

I have been given the task to write a Roulette game, using TCP socket programming in C.
The code was working just fine, until I got close to finishing it, and for some unknown reason, it stopped working properly and I can't track down the error.
The code used to work with simple recv() calls, so I tried making the readn() function (actually got it from another post), however it did not solve the issue.
I might be overlooking the problem, which lies in the for (int i = 0 ; i < max_round ; i++) loop of the main() function.
Here is my server:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
int
readn(int f, void *av, int n)
{
char *a;
int m, t;
a = av;
t = 0;
while(t < n){
m = read(f, a+t, n-t);
if(m <= 0){
if(t == 0)
return m;
break;
}
t += m;
}
return t;
}
typedef struct
{
int _count, _bet, _client, _currency;
int _numbers[3];
char *_color;
} Roulette;
int find_element(int searched, int numbers[], int count)
{
for (int i = 0; i < count; i++)
{
if (searched == numbers[i])
return 1;
}
return 0;
}
void Round_Results(Roulette *obj1, Roulette *obj2, const int size)
{
char *lose_msg = "Sajnos nem nyert ebben a korben!\n";
char *win_msg = "Gratulalok, ebben a korben nyert!\n";
char answer[size];
srand(time(NULL));
int winner_number = rand() % 10;
if ((find_element(winner_number, obj1->_numbers, obj1->_count) == 0) && (find_element(winner_number, obj1->_numbers, obj1->_count) == 0))
{
send(obj1->_client, lose_msg, size, 0);
obj1->_currency = obj1->_currency - obj1->_bet;
printf("%d", obj1->_currency);
sprintf(answer, "%d", obj1->_currency);
send(obj1->_client, answer, size, 0);
send(obj2->_client, lose_msg, size, 0);
obj2->_currency = obj2->_currency - obj2->_bet;
printf("%d", obj2->_currency);
sprintf(answer, "%d", obj2->_currency);
send(obj2->_client, answer, size, 0);
}
else if ((find_element(winner_number, obj1->_numbers, obj1->_count) == 1) && (find_element(winner_number, obj1->_numbers, obj1->_count) == 0))
{
send(obj1->_client, win_msg, size, 0);
obj1->_currency = obj1->_currency + obj1->_bet * (6 / obj1->_count);
printf("%d", obj1->_currency);
sprintf(answer, "%d", obj1->_currency);
send(obj1->_client, answer, size, 0);
send(obj2->_client, lose_msg, size, 0);
obj2->_currency = obj2->_currency - obj2->_bet;
printf("%d", obj2->_currency);
sprintf(answer, "%d", obj2->_currency);
send(obj2->_client, answer, size, 0);
}
else if ((find_element(winner_number, obj1->_numbers, obj1->_count) == 0) && (find_element(winner_number, obj1->_numbers, obj1->_count) == 1))
{
send(obj1->_client, lose_msg, size, 0);
obj1->_currency = obj1->_currency - obj1->_bet;
printf("%d", obj1->_currency);
sprintf(answer, "%d", obj1->_currency);
send(obj1->_client, answer, size, 0);
send(obj2->_client, win_msg, size, 0);
obj2->_currency = obj2->_currency + obj2->_bet * (6 / obj2->_count);
printf("%d", obj2->_currency);
sprintf(answer, "%d", obj2->_currency);
send(obj2->_client, answer, size, 0);
}
else if ((find_element(winner_number, obj1->_numbers, obj1->_count) == 1) && (find_element(winner_number, obj1->_numbers, obj1->_count) == 1))
{
send(obj1->_client, win_msg, size, 0);
obj1->_currency = obj1->_currency + obj1->_bet * (6 / obj1->_count);
printf("%d", obj2->_currency);
sprintf(answer, "%d", obj2->_currency);
send(obj1->_client, answer, size, 0);
send(obj2->_client, win_msg, size, 0);
obj2->_currency = obj2->_currency + obj2->_bet * (6 / obj1->_count);
printf("%d", obj2->_currency);
sprintf(answer, "%d", obj2->_currency);
send(obj2->_client, answer, size, 0);
}
}
void Initialize(int client, int count, int numbers[], int bet, char *color, Roulette *obj)
{
obj->_client = client;
obj->_count = count;
obj->_color = color;
obj->_bet = bet;
for (int i = 0; i < count; i++)
obj->_numbers[i] = numbers[i];
}
void Round_Information(int client, const int size, Roulette *obj)
{
char *message = malloc(size);
char *money_msg = "Mennyi zsetonba fogad?\n";
char *number_msg = "Melyik szamra fogad?\n[0-9]\n";
char *count_msg = "Mennyi szamra fogad?\n[1-3]\n";
char *color_msg = "Milyen szinre fogad?\n[black/red]\n";
int count = 0;
char *color;
int numbers[3];
int bet;
//Bet
send(client, money_msg, size, 0);
readn(client,message,size);
bet = atoi(message);
//Count
send(client, count_msg, size, 0);
readn(client,message,size);
count = atoi(message);
//Number/Numbers
for (int i = 0; i < count; i++)
{
send(client, number_msg, size, 0);
readn(client,message,size);
numbers[i] = atoi(message);
}
//Color
send(client, color_msg, size, 0);
readn(client,message,size);
color = message;
Initialize(client, count, numbers, bet, color, obj);
free(message);
return 0;
}
int main(int argc, char **argv)
{
if (argc < 2)
{
printf("tul keves argumentum!\nusage : ./valami PORT_NR\n");
exit(-1);
}
const int size = 50;
int max_round, starting_money;
int flag = 0;
int on = 1;
char *message = malloc(size);
char *round_msg = "Korok szama :\n";
char *greeting_msg = "Sikeresen csatlakozott a szerverre!\n";
char *waiting_msg = "A masik jatekosra varunk!\n";
char *win_msg = "Gratulalok !\nMegnyerte a jatekot!\n";
char *lose_msg = "Jatek vege !\nSajnos nem nyert!\n";
Roulette *obj1 = malloc(size);
Roulette *obj2 = malloc(size);
int server_socket = socket(AF_INET, SOCK_STREAM, flag);
if (server_socket < 0)
{
printf("Nem sikerult a socket-et letrehozni\n");
exit(-1);
}
struct sockaddr_in server_adress;
server_adress.sin_addr.s_addr = INADDR_ANY;
server_adress.sin_family = AF_INET;
server_adress.sin_port = atoi(argv[1]);
setsockopt(server_socket, SOL_SOCKET, SO_KEEPALIVE, (char *)&on, sizeof(on));
setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&on, sizeof(on));
int binding_server = bind(server_socket, (struct sockaddr *)&server_adress, sizeof(server_adress));
if (binding_server < 0)
{
printf("nem sikerult bindolni a szervert!\n");
exit(-1);
}
listen(server_socket, 2);
int client1 = accept(server_socket, NULL, NULL);
int client2 = accept(server_socket, NULL, NULL);
send(client1, greeting_msg, size, flag);
send(client2, greeting_msg, size, flag);
printf("Milyen hosszu legyen a jatek ? (Hany kor)\n");
scanf("%s", message);
max_round = atoi(message);
//Korok szama
send(client1, message, size, flag);
send(client2, message, size, flag);
printf("Mennyi zsetonnal kezdodjon a jatek?\n");
scanf("%s", message);
starting_money = atoi(message);
//Kezdo penz
send(client1, message, size, flag);
send(client2, message, size, flag);
obj1->_currency = starting_money;
obj2->_currency = starting_money;
for (int i = 0; i < max_round; i++)
{
Round_Information(client1, size, obj1);
Round_Information(client2, size, obj2);
Round_Results(obj1, obj2, size);
}
if (obj1->_currency > obj2->_currency)
{
send(obj1->_client, win_msg, size, flag);
send(obj2->_client, lose_msg, size, flag);
}
else if (obj1->_currency < obj2->_currency)
{
send(obj2->_client, win_msg, size, flag);
send(obj1->_client, lose_msg, size, flag);
}
else
{
send(obj1->_client, lose_msg, size, flag);
send(obj2->_client, lose_msg, size, flag);
}
close(client1);
close(client2);
close(server_socket);
free(message);
free(obj1);
free(obj2);
return 0;
}
Here is the Client:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
void Round_Information(int client, const int size, int currency)
{
char *message = malloc(size);
char answer[size];
char *black = "black";
char *red = "red";
int count = 0;
memset(answer, 0, size);
//Bet
recv(client, message, size, 0);
if (currency == 0)
{
printf("Game over!\nVeszitett!\n");
close(client);
}
while (atoi(answer) < 1 || atoi(answer) > currency)
{
if (strcmp(answer, "befejeztem"))
{
close(client);
}
printf("%s", message);
scanf("%s", answer);
}
if (strcmp(answer, "befejeztem"))
{
close(client);
}
send(client, answer, size, 0);
answer[0] = '0';
//Count
recv(client, message, size, 0);
while (atoi(answer) < 1 || atoi(answer) > 3)
{
if (strcmp(answer, "befejeztem"))
{
close(client);
}
printf("%s", message);
scanf("%s", answer);
}
count = atoi(answer);
if (strcmp(answer, "befejeztem"))
{
close(client);
}
send(client, answer, size, 0);
//Number/Numbers
for (int i = 0; i < count; i++)
{
recv(client, message, size, 0);
answer[0] = 'z';
while (atoi(answer) <= 0 || atoi(answer) > 9)
{
if (strcmp(answer, "befejeztem"))
{
close(client);
}
printf("%s", message);
scanf("%s", answer);
}
if (strcmp(answer, "befejeztem"))
{
close(client);
}
send(client, answer, size, 0);
}
//Color
recv(client, message, size, 0);
while ((strcmp(answer, black) != 0) && (strcmp(answer, red) != 0))
{
if (strcmp(answer, "befejeztem"))
{
close(client);
}
printf("%s", message);
scanf("%s", answer);
}
if (strcmp(answer, "befejeztem"))
{
close(client);
}
send(client, answer, size, 0);
free(message);
}
void Round_Results(int client_socket, char *message, const int size, int *currency)
{
recv(client_socket, message, size, 0);
printf("%s\n", message);
recv(client_socket, message, size, 0);
(*currency) = atoi(message);
}
int main(int argc, char **argv)
{
if (argc < 2)
{
printf("tul keves argumentum!\nusage : ./valami PORT_NR\n");
exit(-1);
}
const int size = 50;
int flag = 0;
int max_round, currency;
int on = 1;
char message[size];
int client_socket = socket(AF_INET, SOCK_STREAM, flag);
if (client_socket < 0)
{
printf("Nem sikerult a socketet letrehozni!\n");
exit(-1);
}
struct sockaddr_in server_adress;
server_adress.sin_addr.s_addr = INADDR_ANY;
server_adress.sin_family = AF_INET;
server_adress.sin_port = atoi(argv[1]);
setsockopt(client_socket, SOL_SOCKET, SO_KEEPALIVE, (char *)&on, sizeof(on));
setsockopt(client_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&on, sizeof(on));
int connection = connect(client_socket, (struct sockaddr *)&server_adress, sizeof(server_adress));
if (connection < 0)
{
printf("Nem sikerult kapcsolodni a szerverhez!\n");
exit(-1);
}
//Sikeres kapcsolodas
int receive = recv(client_socket, message, size, flag);
if (receive < 0)
{
printf("Nem sikerult megkapni az uzenetet!\n");
exit(-1);
}
printf("%s", message);
//Korok szama
receive = recv(client_socket, message, size, flag);
if (receive < 0)
{
printf("Nem sikerult megkapni az uzenetet!\n");
exit(-1);
}
printf("Korok szama :%s\n", message);
max_round = atoi(message);
//Kezdo penz
receive = recv(client_socket, message, size, flag);
if (receive < 0)
{
printf("Nem sikerult megkapni az uzenetet!\n");
exit(-1);
}
printf("Jelenlegi zsetonok mennyisege :%s\n", message);
currency = atoi(message);
for (int i = 0; i < max_round; i++)
{
Round_Information(client_socket, size, currency);
Round_Results(client_socket, message, size, &currency);
printf("Jelenlegi zseton :%d\n", currency);
}
recv(client_socket, message, size, flag);
printf("%s\n", message);
close(client_socket);
return 0;
}

Answer 1

It was not easy to read, since i do not know what the outputs mean, but i think i found your problem.
if (strcmp(answer, "befejeztem"))
{
close(client);
}
strcmp is 0 when the strings are equal. That means in almost every case you close the socket. Actually in the first loop answer is zero that means you are closing the socket right away. If you close the socket but the server tries to send data the program will receive the SIGPIPE signal and i think the default handler will just abort the program.
Try to change all these if statements to:
if(!strcmp(answer, "befejeztem"))
{
close(client);
}