please help review epoll networking code

[lovecreatesbeauty]

1. How does the code handle EPOLLIN, EPOLLOUT, EPOLLERR this way?

for (iefd = 0; iefd != nefd; iefd++){
if (evp[iefd].data.fd == sfd) {
...
} else {

if ((evp[iefd].events & EPOLLIN) == EPOLLIN){
...
}

if ((evp[iefd].events & EPOLLOUT) == EPOLLOUT){
...
}

if ((evp[iefd].events & EPOLLERR) == EPOLLERR ||
(evp[iefd].events & EPOLLHUP) == EPOLLHUP ||
((evp[iefd].events & EPOLLIN) != EPOLLIN && (evp[iefd].events & EPOLLOUT) != EPOLLOUT))
{
...
}

2. Do I need to use epoll functions on client side which calls connect()?

I see some select() example which applies select functions on both server and client sides.


Thank you for your time!


////////////////////////////////////////////////////////////////////////////////
// server.c
// 16288...@qq.com
////////////////////////////////////////////////////////////////////////////////

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <stdlib.h>

#define PORTNO "12345"
#define BACKLOG 5
#define MAXEVENTS 10

int setnonblocking(int fd)
{
int flags;

flags = fcntl(fd, F_GETFL, 0);
if (flags == -1){
perror ("fcntl");
return -1;
}
flags |= O_NONBLOCK;
flags = fcntl(fd, F_SETFL, flags);
if (flags == -1){
perror ("fcntl");
return -1;
}
return 0;
}

int main(void)
{
struct addrinfo hints, *result, *rp;
struct sockaddr addr;
socklen_t addrlen;
int sfd, ifd;
int optval;
int rt, errsv = 0;
char host[NI_MAXHOST], service[NI_MAXSERV];
char buf[128] = {'\0'};
struct epoll_event ev, *evp;
int efd, iefd, nefd;
char hostnm[20] = {'\0'};
time_t tm;

if (gethostname(hostnm, sizeof hostnm - 1) == -1){
perror("gethostname");
return -1;
}

memset(&hints, 0, sizeof hints);
hints.ai_canonname = NULL;
hints.ai_addr = NULL;
hints.ai_next = NULL;
hints.ai_socktype = SOCK_STREAM;
hints.ai_family = AF_UNSPEC;
hints.ai_flags = AI_PASSIVE | AI_NUMERICSERV;

rt = getaddrinfo(NULL, PORTNO, &hints, &result);
errsv = errno;
if (rt){
printf("%s: %s\n", "getaddrinfo gai_strerror", gai_strerror(rt));
if (errsv)
perror("getaddrinfo");
return rt;
}

optval = 1;
for (rp = result; rp; rp = rp->ai_next){
sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (sfd == -1)
continue;
if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof optval) == -1){
perror("setsockopt");
return -1;
}
if (!bind(sfd, rp->ai_addr, rp->ai_addrlen))
break;
close(sfd);
}
if (!rp){
printf("Could not bind socket to any address\n");
return !rp;
}

if (listen(sfd, BACKLOG) == -1){
perror("listen");
return -1;
}
freeaddrinfo(result);

efd = epoll_create1(0);
if (efd == -1){
perror("epoll_create");
return -1;
}
ev.events = EPOLLIN | EPOLLOUT | EPOLLET;
ev.data.fd = sfd;
if (epoll_ctl(efd, EPOLL_CTL_ADD, sfd, &ev) == -1){
perror("epoll_ctl");
return -1;
}
errsv = 0;
evp = calloc(MAXEVENTS, sizeof ev);
errsv = errno;
if (!evp){
printf("%s: %s\n", "calloc failed ", errsv ? strerror(errsv) : "");
return !evp;
}

for (;;){
nefd = epoll_wait(efd, evp, MAXEVENTS, -1);
if (nefd == -1){
perror("epoll_wait");
return -1;
}

for (iefd = 0; iefd != nefd; iefd++){
if (evp[iefd].data.fd == sfd) {
addrlen = sizeof addr;
ifd = accept(sfd, &addr, &addrlen);
if (ifd == -1){
perror("accept");
return -1;
}
if (!getnameinfo(&addr, addrlen, host, NI_MAXHOST, service, NI_MAXSERV, 0))
printf("Connection from %s %s\n", host, service);
else
printf("Unknown %s %s\n", host, service);
if (setnonblocking(ifd)){
printf("setnonblocking failed\n");
return -1;
}
ev.events = EPOLLIN | EPOLLOUT | EPOLLET;
ev.data.fd = ifd;
if (epoll_ctl(efd, EPOLL_CTL_ADD, ifd, &ev) == -1){
perror("epoll_ctl");
return -1;
}
} else {
if ((evp[iefd].events & EPOLLIN) == EPOLLIN){
memset(buf, 0, sizeof buf);

//partial read or recv? not handled
rt = recv(evp[iefd].data.fd, buf, sizeof buf - 1, 0); //MSG_DONTWAIT
errsv = errno;
if (rt == -1){
printf("%s: %s\n", "recv", strerror(errsv));
if (errsv == ECONNRESET || errsv == ENOTCONN){
close(evp[iefd].data.fd);
continue;
}
}
if (rt == 0){
printf("%s: %s\n", "recv", "Peer has performed an orderly shutdown");
close(evp[iefd].data.fd);
continue;
}
if (strlen(buf))
printf("recv: client time: %d %s", strlen(buf), buf);
}

if ((evp[iefd].events & EPOLLOUT) == EPOLLOUT){
time(&tm);
snprintf(buf, sizeof buf, "%s %s", hostnm, ctime(&tm));

//partial write or send? not handled
rt = send(evp[iefd].data.fd, buf, strlen(buf), 0); //MSG_DONTWAIT
errsv = errno;
if (rt == -1){
printf("%s: %s\n", "send", strerror(errsv));
if (errsv == ECONNRESET || errsv == ENOTCONN || errsv == EPIPE || errsv == EBADF){
close(evp[iefd].data.fd);
continue;
}
}
}

if ((evp[iefd].events & EPOLLERR) == EPOLLERR ||
(evp[iefd].events & EPOLLHUP) == EPOLLHUP ||
((evp[iefd].events & EPOLLIN) != EPOLLIN && (evp[iefd].events & EPOLLOUT) != EPOLLOUT))
{
printf ("Unknown event: %d\n", evp[iefd].events);
close (evp[iefd].data.fd);
continue;
}
}
}
}

// not reachable
free(evp);
close(sfd);
return 0;
}


////////////////////////////////////////////////////////////////////////////////
// client.c
// 16288...@qq.com
////////////////////////////////////////////////////////////////////////////////

#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#define PORTNO "12345"

int main(int argc, char *argv[])
{
struct addrinfo hints, *result, *rp;
int fd;
int rt;
int errsv = 0;
char buf[128] = {'\0'};
time_t tm;
char hostnm[20] = {'\0'};

if (argc < 2){
printf("%s <host>\n", argv[0]);
return -1;
}
if (gethostname(hostnm, sizeof hostnm - 1) == -1){
perror("gethostname");
return -1;
}

memset(&hints, 0, sizeof hints);
hints.ai_canonname = NULL;
hints.ai_addr = NULL;
hints.ai_next = NULL;
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE | AI_NUMERICSERV;

rt = getaddrinfo(argv[1], PORTNO, &hints, &result);
errsv = errno;
if (rt){
printf("%s: %s\n", "getaddrinfo gai_strerror", gai_strerror(rt));
if (errsv)
perror("getaddrinfo");
return rt;
}
for (rp = result; rp; rp = rp->ai_next){
fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (fd == -1)
continue;
if (connect(fd, rp->ai_addr, rp->ai_addrlen) != -1)
break;
close(fd);
}
if (!rp){
printf("Could not connect socket to any address\n");
return !rp;
}
freeaddrinfo(result);

for (;;){

sleep(1); //Block revc / send used - no MSG_DONTWAIT
//temporary for demo only
//Normal code does not require this sleep.

// send
time(&tm);
snprintf(buf, sizeof buf, "%s %s", hostnm, ctime(&tm));
rt = send(fd, buf, strlen(buf), 0); //MSG_DONTWAIT
errsv = errno;
if (rt == -1){
printf("%s: %s\n", "send", strerror(errsv));
if (errsv == ECONNRESET || errsv == ENOTCONN || errsv == EPIPE){
close(fd);
break;
}
}

// recv
memset(buf, 0, sizeof buf);
rt = recv(fd, buf, sizeof buf - 1, 0); //MSG_DONTWAIT
errsv = errno;
if (rt == -1){
printf("%s: %s\n", "recv", strerror(errsv));
if (errsv == ECONNRESET || errsv == ENOTCONN){
close(fd);
break;
}
}
if (rt == 0){
close(fd);
printf("%s: %s\n", "recv", "Peer has performed an orderly shutdown");
break;
}
if (strlen(buf))
printf("recv: server time: %d %s", strlen(buf), buf);
}
close(fd);
return 0;
}

[Jorgen Grahn]

On Thu, 2012-08-30, lovecreatesbeauty wrote:
...
> 2. Do I need to use epoll functions on client side which calls connect()?
>
> I see some select() example which applies select
> functions on both server and client sides.

Select and epoll (which is Linux-specific, by the way) are used for
the same kinds of things.

Look at all your system calls which may block for a long time. Ask
yourself for each one "is it ok if I block here for a minute?". If
the answer is "yes" you don't need select/epoll.

/Jorgen

--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .