Chatting server using epoll - unexpected behavior - c

Question

I'm working on writing a simple chatting server-client C program using epoll. I'm writing and testing it in Xubuntu, and I found something strange. Message from server to client is delivered well. But Message from client to server is delivered at the moment when I push enter key at 'SERVER SIDE(putty window)'
For example, if I type 'Hello World' in the client window and push enter key, the message doesn't show on the server side, however, when I push enter key on the server side, 'Hello World' shows on the window!
I think something is wrong in server.c but I can't find what's wrong. I used epoll and let it monitor EPOLLIN|EPOLLOUT to receive and send messages.
In other hand, I wrote client program with multi-threading.
Full src are below without header.
Any comment will be appreciated. Thank you!
server.c
int main(int argc, char *argv[])
{
int serv_sock, clnt_sock;
struct sockaddr_in serv_adr, clnt_adr;
socklen_t adr_sz;
int str_len, i;
char buf[BUF_SIZE];
struct epoll_event *ep_events;
struct epoll_event event;
int epfd, event_cnt;
if(argc!=2) {
printf("Usage : %s <port>\n", argv[0]);
exit(1);
}
serv_sock=socket(PF_INET, SOCK_STREAM, 0);
memset(&serv_adr, 0, sizeof(serv_adr));
serv_adr.sin_family=AF_INET;
serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
serv_adr.sin_port=htons(atoi(argv[1]));
if(bind(serv_sock, (struct sockaddr*) &serv_adr, sizeof(serv_adr))==-1)
error_handling("bind() error");
if(listen(serv_sock, 5)==-1)
error_handling("listen() error");
epfd=epoll_create(EPOLL_SIZE);
ep_events=malloc(sizeof(struct epoll_event)*EPOLL_SIZE);
//set_nonblocking_mode(serv_sock);
event.events=EPOLLIN;
event.data.fd=serv_sock;
epoll_ctl(epfd, EPOLL_CTL_ADD, serv_sock, &event);
while(1) {
event_cnt=epoll_wait(epfd, ep_events, EPOLL_SIZE, -1);
if(event_cnt==-1) {
puts("epoll_wait() error");
break;
}
for(i=0; i<event_cnt; i++) {
if(ep_events[i].data.fd==serv_sock) {
adr_sz=sizeof(clnt_adr);
clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr, &adr_sz);
//set_nonblocking_mode(clnt_sock);
event.events=EPOLLIN|EPOLLOUT;
event.data.fd=clnt_sock;
epoll_ctl(epfd, EPOLL_CTL_ADD, clnt_sock, &event);
printf("connected client: %d \n", clnt_sock);
}
else {
if((ep_events[i].events & EPOLLIN) == EPOLLIN) {
memset(buf, 0, BUF_SIZE);
str_len=read(ep_events[i].data.fd, buf, BUF_SIZE-1);
buf[str_len] = 0;
if(str_len==0) { // close request!
epoll_ctl(epfd, EPOLL_CTL_DEL, ep_events[i].data.fd, NULL);
close(ep_events[i].data.fd);
printf("closed client: %d \n", ep_events[i].data.fd);
}
/*
else if(str_len < 0) {
if(errno == EAGAIN)
break;
}*/
else {
fputs(buf, stdout);
}
}
if((ep_events[i].events & EPOLLOUT) == EPOLLOUT) {
fgets(buf, BUF_SIZE, stdin);
if(!strcmp(buf, "q\n") || !strcmp(buf, "Q\n")) {
epoll_ctl(epfd, EPOLL_CTL_DEL, ep_events[i].data.fd, NULL);
close(ep_events[i].data.fd);
printf("closed client: %d \n", ep_events[i].data.fd);
}
else {
write(ep_events[i].data.fd, buf, strlen(buf));
}
}
}
}
}
close(serv_sock);
close(epfd);
return 0;
}
void set_nonblocking_mode(int fd)
{
int flag = fcntl(fd, F_GETFL, 0);
fcntl(fd, F_SETFL, flag|O_NONBLOCK);
}
void error_handling(char *buf)
{
fputs(buf, stderr);
fputc('\n', stderr);
exit(1);
}
client.c
void * send_msg(void * arg);
void * recv_msg(void * arg);
void error_handling(char * msg);
char name[NAME_SIZE]="[DEFAULT]";
char msg[BUF_SIZE];
int main(int argc, char *argv[])
{
int sock;
struct sockaddr_in serv_addr;
pthread_t snd_thread, rcv_thread;
void * thread_return;
if(argc!=4) {
printf("Usage : %s <IP> <port> <name>\n", argv[0]);
exit(1);
}
sprintf(name, "[%s]", argv[3]);
sock=socket(PF_INET, SOCK_STREAM, 0);
memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family=AF_INET;
serv_addr.sin_addr.s_addr=inet_addr(argv[1]);
serv_addr.sin_port=htons(atoi(argv[2]));
if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1)
error_handling("connect() error");
pthread_create(&snd_thread, NULL, send_msg, (void*)&sock);
pthread_create(&rcv_thread, NULL, recv_msg, (void*)&sock);
pthread_join(snd_thread, &thread_return);
pthread_join(rcv_thread, &thread_return);
close(sock);
return 0;
}
void * send_msg(void * arg) // send thread main
{
int sock=*((int*)arg);
char name_msg[NAME_SIZE+BUF_SIZE];
while(1)
{
fgets(msg, BUF_SIZE, stdin);
if(!strcmp(msg,"q\n")||!strcmp(msg,"Q\n"))
{
close(sock);
exit(0);
}
sprintf(name_msg,"%s %s", name, msg);
write(sock, name_msg, strlen(name_msg));
}
return NULL;
}
void * recv_msg(void * arg) // read thread main
{
int sock=*((int*)arg);
char name_msg[NAME_SIZE+BUF_SIZE];
int str_len;
while(1)
{
str_len=read(sock, name_msg, NAME_SIZE+BUF_SIZE-1);
if(str_len==-1)
return (void*)-1;
name_msg[str_len]=0;
fputs(name_msg, stdout);
}
return NULL;
}
void error_handling(char *msg)
{
fputs(msg, stderr);
fputc('\n', stderr);
exit(1);
}