system V semaphores C - c

Question

I’m trying to use the system V semaphores, but I'm not able to control their value with semop, and so what they do. I should have three total processes that alternate with each other with semaphores that regulate the game turns. If anyone can help me with a practical example I would be very grateful.
PROCESS1
#include <sys/types.h>
#include <sys/ipc.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/sem.h>
#define KSEM 2292
#define KKSEM 9922
int main(int argc, char *argv[]){
struct sembuf x;
x.sem_num = 0;
x.sem_op = -1;
x.sem_flg = 0;
int idserver, idclient;
int val1 = 0, val2 = 0;
// declaration
idserver = semget (KSEM, 1, IPC_CREAT | IPC_EXCL | 0666);
idclient = semget (KKSEM, 1, IPC_CREAT | IPC_EXCL | 0666);
if (idserver <0){
perror("idserver: ");
_exit(1);
}
if (idclient <0){
perror("idclient: ");
_exit(1);
}
printf("hello1");
// intializing
semctl(idserver, 0, SETVAL, val1); //server set to 0
semctl(idclient, 0, SETVAL, val2); //client set to 0
printf("ciaoserver1");
int a;
a = semop (idserver, &x, 1);
printf("waiting for client...");
printf("VALUE SERVER: %i \n", a);
return 0;
}
PROCESS2
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/sem.h>
#define KSEM 2292
#define KKSEM 9922
int main(int argc, char *argv[]){
struct sembuf x;
x.sem_num = 0;
x.sem_op = 1;
x.sem_flg = 0;
struct sembuf y;
y.sem_num = 0;
y.sem_op = 0;
y.sem_flg = 0;
struct sembuf z;
y.sem_num = 0;
y.sem_op = -2;
y.sem_flg = 0;
int idserver, idclient;
int val1 = 0, val2 = 0;
// declaration
idserver = semget (KSEM, 1, IPC_EXCL | 0666);
if(idserver < 0) {
perror("idserver: ");
_exit(1);
}
idclient = semget (KKSEM, 1, IPC_EXCL | 0666);
if(idclient<0){
perror("idclient: ");
_exit(1);
}
// initialize
semctl(idserver, 0, SETVAL, val1); //server set to 0
semctl(idclient, 0, SETVAL, val2); //client set to 0
printf("CLIENT1");
int a;
a = semop (idclient, &x, 1);
semop (idclient, &y, 1);
semop (idclient, &x, 1);
semop (idclient, &y, 1);
semop (idserver, &y, 1);
printf("VALUE CLIENT 1: %i", a);
return 0;
}