my server pauses at no reason until I kill the client - c

Question

when i run both client and server i get this as result:
on server
Server is on
Client: XXX.X.X.X accepted
(that's the point that the program pauses until I type ctrl+C in client)
I try to get in while
I get in while
Client
AI Choise:Scissor
AI:Wins ratio 0,Looses ratio 0,Ties ratio 1
I get in while
Client
AI Choise:Scissor
AI:Wins ratio 0,Looses ratio 0,Ties ratio 2
on client
1)--> Paper
2)--> Scissor
3)--> Rock
4)--> Quit
^C
my code:
Server:
int main(int argc, char *argv[]){
printf("\nServer is on\n");
int sockfd, newsockfd, portno;
socklen_t clilen;
int Client_Choice;
struct sockaddr_in serv_addr, cli_addr;
int n,Who_Wins;
int ai_wins=0,ai_looses=0,ties=0,total=0,ai_win_ratio=0,ai_looses_ratio=0,ai_ties_ratio;
time_t t;
srand((unsigned) time(&t));
if (argc < 2) {
fprintf(stderr,"\nERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0){
error("\nERROR opening socket\n",sockfd);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0){
error("\nERROR on binding\n",sockfd);
}
listen(sockfd,5);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr,&clilen);
if (newsockfd < 0){
error("\nERROR on accept\n",sockfd);
}
char *cli_IP = malloc(sizeof(cli_addr.sin_addr.s_addr));
if (!cli_IP){
error("\nCould not allocate memory for conversion.\n",sockfd);
}
inet_ntop( AF_INET , &cli_addr.sin_addr.s_addr , cli_IP , INET_ADDRSTRLEN );
printf("\nClient: %s accepted\n",cli_IP);
printf("I try to get in while");
while(Client_Choice!=4){
printf("I get in while");
n= read( newsockfd, &Client_Choice, sizeof(Client_Choice) );
if(n < 0) {
error("\nERROR reading from socket\n",sockfd);
}
.
.
.
}
close(newsockfd);
close(sockfd);
return 0;
}
client
int main(int argc, char *argv[]){
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
int send;
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {
error("ERROR opening socket\n");
}
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr,server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) {
error("ERROR connecting\n");
}
while(send < 1 ||send > 4){
printf("\n\t1)--> Paper\n\t2)--> Scissor\n\t3)--> Rock\n\t4)--> Quit\n");
scanf("%d",&send);
n = write(sockfd,&send,sizeof(send));
if (n < 0){
error("ERROR writing to socket\n");
}
n = read(sockfd,&send,sizeof(send));
if (n == 0){
error("ERROR reading from socket\n");
}
}
close(sockfd);
return 0;
}

Answer 1

Your server is blocked waiting the message from the client. You have not reserved resources for dealing with several clients and only have a single process serving a single client (using the connection socket from accept(2)). That's the reason of it to appear blocking. In a normal server scenario, a new process is spawned by a fork(2) system call to deal with the socket obtained from accept(2) while the main process continues to accept(2) connections on the socket used for accepting new connections. As you are dealing with two sockets in server, but not attending the socket descriptor where accept(2) connections come in, it appears to be blocked, but it is actually ready to accept the commands from the active client. This is what is called a sequential server (it doesn't allow a connection before the first one terminates).
By the way, send is uninitialized before use in first while (send < 1 || send > 4) sentence so in case you get it casually equal to 2 (for example) you won't get client code into the while at all. This is only a point, probably there will be more. Why have you used different names for the message type interchanged between server and client? this makes more difficult to search for errors.