multiple clients stop and wait with C & UDP - c

Question

I am implementing stop&wait with c and udp socket programming. with one client it works but with more than one client it dosen't work.
server.c
struct sockaddr_in newAddr;
socklen_t addr_size = sizeof(newAddr);
fd_set rset;
int frame_id = 0;
Frame frame_recv;
Frame frame_send;
int socket_desc = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (socket_desc < 0) {
perror("Socket Creation Failed ");
exit(EXIT_FAILURE);
}
else {
perror("Socket Created ");
}
if (bind(socket_desc, (struct sockaddr *) &server_addr,
sizeof(server_addr)) < 0 ) {
perror("Bind Failed ");
exit(EXIT_FAILURE);
}
else {
perror("Bind Done ");
}
printf("Listening for Messages...\n");
FD_ZERO(&rset);
while (1) {
FD_SET(socket_desc, &rset);
select(socket_desc + 1, &rset, NULL, NULL, NULL);
if (FD_ISSET(socket_desc, &rset)) {
int recv_size = recvfrom(socket_desc, &frame_recv, sizeof(Frame), 0,
(struct sockaddr *) &newAddr, &addr_size);
if (recv_size > 0 && frame_recv.frame_kind == 1 &&
frame_recv.sq_no == frame_id) {
printf("[+]Frame Received: %s\n", frame_recv.packet.data);
frame_send.sq_no = 0;
frame_send.frame_kind = 0;
frame_send.ack = frame_recv.sq_no + 1;
sendto(socket_desc, &frame_send, sizeof(frame_send), 0,
(struct sockaddr*)&newAddr, addr_size);
printf("[+]Ack Send\n");
}
else {
printf("[+]Frame Not Received\n");
break;
}
frame_id ++;
}
}
close(socket_desc);
client.c
char buffer[1024];
socklen_t addr_size;
int frame_id = 0;
Frame frame_send;
Frame frame_recv;
int ack_recv = 1;
int socket_desc = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (socket_desc < 0) {
perror("Socket Creation Failed ");
exit(EXIT_FAILURE);
}
else {
perror("Socket Created ");
}
while (1) {
if (ack_recv == 1) {
frame_send.sq_no = frame_id;
frame_send.frame_kind = 1;
frame_send.ack = 0;
printf("Enter Data: ");
scanf("%s", buffer);
strcpy(frame_send.packet.data, buffer);
sendto(socket_desc, &frame_send, sizeof(Frame), 0,
(struct sockaddr*)&server_addr, sizeof(server_addr));
printf("[+]Frame Send\n");
}
int addr_size = sizeof(server_addr);
int recv_size = recvfrom(socket_desc, &frame_recv, sizeof(frame_recv), 0 ,(struct sockaddr*)&server_addr, &addr_size);
if (recv_size > 0 && frame_recv.sq_no == 0 && frame_recv.ack == frame_id + 1) {
printf("[+]Ack Received\n");
ack_recv = 1;
}
else {
printf("[-]Ack Not Received\n");
ack_recv = 0;
break;
}
frame_id++;
}
close(socket_desc);
header.h
typedef struct packet {
char data[1024];
} Packet;
typedef struct frame {
int frame_kind; //ACK:0, SEQ:1 FIN:2
int sq_no;
int ack;
Packet packet;
} Frame;
I found that frame_recv.sq_no and frame_id have different value when the second client run.
I read questions with same topic, but could not find out the error from my code.