I have a server that is using epoll. My question is what is the best way to process all the buffers so I can deal with half messages, or multiple messages coming in a buffer.
For example:
If the message is "Hello From Client Number #".
Buffer's received through epoll:
From Client 1: "Hello From"
From Client 2: "Hello From Client Number 2Hello From Client Number 2"
From Client 1: " Client Number 1HelloFromClient Number 1"
In this scenario, I need to be able to identify that "Hello From" is only half a message and store it somewhere. Then I need to be able to process that two whole messages have gone through from Client 2. And then go back and pick up where I left off from Client 1. I know there are ways of distinguishing messages using delimiters, or sending message length, but I'm not quit sure on how to deal with receiving half a message at all.
Does anyone have any ideas, or any sample code I could look at.
Note I know it's bad that I'm currently processing everything into one buffer. I'm going to change that. Would I need a separate buffer for each client?
Thanks for any help!
void epoll(int listening_port)
{
char buffer[500]; //buffer for message
int listen_sock = 0; //file descriptor (fd) for listening socket
int conn_sock = 0; //fd for connecting socket
int epollfd = 0; // fd for epoll
int nfds = 0; //number of fd's ready for i/o
int i = 0; //index to which file descriptor we are lookng at
int curr_fd = 0; //fd for socket we are currently looking at
bool loop = 1; //boolean value to help identify whether to keep in loop or not
socklen_t address_len;
struct sockaddr_in serv_addr;
struct epoll_event ev, events[EPOLL_MAX_EVENTS];
ssize_t result = 0;
bzero(buffer, sizeof(buffer));
bzero(&serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = listening_port;
serv_addr.sin_addr.s_addr = INADDR_ANY;
listen_sock = create_socket();
if(bind(listen_sock, SA &serv_addr, sizeof(serv_addr)) != 0)
{
perror("Bind failed");
}
else
{
printf("Bind successful\n");
}
set_socket_nonblocking(listen_sock);
listen_on_socket(listen_sock, SOMAXCONN); //specifying max connections in backlog
epollfd = initialize_epoll();
ev.events = EPOLLIN | EPOLLOUT | EPOLLET | EPOLLRDHUP;
ev.data.fd = listen_sock;
if(epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == ERROR)
{
perror("Epoll_ctl: listen sock");
}
else
{
printf("Successfully added listen socket to epoll\n");
}
while (RUN_EPOLL)
{
nfds = epoll_wait(epollfd, events, EPOLL_MAX_EVENTS, 0); //waiting for incoming connection;
if(nfds == ERROR)
{
perror("EPOLL_Wait");
}
//printf("Finished waiting\i");
for(i = 0; i < nfds; ++i)
{
curr_fd = events[i].data.fd;
loop = true; //reset looping flag
//Notification from Listening Socket - Process Incoming Connections
if (curr_fd == listen_sock) {
while(loop)
{
conn_sock = accept(listen_sock, SA &serv_addr, &address_len); //accept incoming connection
printf("Accepted new incoming connection - socket fd: %d\n", conn_sock);
if (conn_sock > 0) //if successful set socket nonblocking and add it to epoll
{
set_socket_nonblocking(conn_sock);
ev.events = EPOLLIN | EPOLLOUT| EPOLLET | EPOLLRDHUP; //setting flags
ev.data.fd = conn_sock; //specify fd of new connection in event to follow
if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock, &ev) == ERROR) //add fd to monitored fd's
{
perror("epoll_ctl: conn_sck");
}
else
{
printf("Added %d to monitor list\n", conn_sock);
}
}
else if (conn_sock == ERROR)
{
if ((errno == EAGAIN) || (errno == EWOULDBLOCK))
{
printf("All incoming connections processed\n");
loop = false;
}
else
{
perror("Accept remote socket");
loop = false;
}
}
}
}
else if(events[i].events & EPOLLRDHUP) //detecting if peer shutdown
{
printf("Detected socket peer shutdown. Closing now. \n");
if (epoll_ctl(epollfd, EPOLL_CTL_DEL, curr_fd, NULL) == ERROR) {
perror("epoll_ctl: conn_sck");
}
close_socket(curr_fd);
}
else if(events[i].events & EPOLLIN)
{
while(loop)
{
result = recv(curr_fd, buffer, sizeof(buffer), 0);
//printf("Length of incoming message is %d\i", result);
if(result > 0) //
{
printf("File Descriptor: %d. Message: %s\n", curr_fd, buffer); //I know this will need to be changd
bzero(buffer, sizeof(buffer));
}
else if(result == ERROR) //Message is completely sent
{
if(errno == EAGAIN)
{
loop = false;
}
}
else if(result == 0)
{
//Removing the fd from the monitored descriptors in epoll
if (epoll_ctl(epollfd, EPOLL_CTL_DEL, curr_fd, NULL) == ERROR) {
perror("epoll_ctl: conn_sck");
}
close_socket(curr_fd); //Closing the fd
loop = false;
}
}
}
}
}
close_socket(listen_sock);
//need to develop way to gracefully close out of epoll
return;
}
