poll()このプログラムは、ポート8888でTelnet接続を受け入れ、send()を使用して各Telnetクライアントからメッセージを送信するrecv()ことになっていますが、100％は機能しません。特定の接続は常に誰にでもメッセージを送信でき、プログラムは正常に機能しているようですが、メッセージを送信できないクライアントが少なくとも1人は常に存在します。すべてのクライアントは常に受信できます（pollは受信データを登録しません）。
このコードはそれ自体で実行されるため、ファイルに入れてコンパイルするとgcc -o app filename.c、ポート8888でローカルホストにtelnetで接続し、機能しないことを確認できます。このコードはFedora用に書かれていますが、Linux固有以外のものを含めるべきではありません。どんな助けでも本当にありがたいです。
#include <stdio.h>
#include <stdlib.h>
#include <poll.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#define PORT 8888
#define MAX_CONN 10
#define SECOND 1000
#define TIMEOUT (30 * SECOND)
static int listen_socket();
int main(int argc, char **argv)
{
struct pollfd **my_fds; //array of pollfd structures for poll()
struct pollfd *curr, *new_conn; //so I can loop through
int num_fds; //count of how many are being used
int i, j; //for loops
char buff[255], buff2[255]; //for sending and recieving text
struct sockaddr_in my_addr, their_addr; // my address information
socklen_t sin_size;
int buff_sz; //size of data recieved
printf("App Started\n");
//allocate space for 10
my_fds = (struct pollfd**) malloc(sizeof(struct pollfd*) * MAX_CONN);
//set all the pointers to NULL
for (i = 0; i < MAX_CONN; i++)
*(my_fds + i) = NULL;
//I call listen_socket() which creates a socket to listen to
//this is anchored into my_fds array at element 0.
curr = (struct pollfd*) malloc (sizeof(struct pollfd));
curr->fd = listen_socket();
curr->events = POLLIN;
curr->revents = 0;
*my_fds = curr;
printf("Listening socket fd locked always at position zero in array: %d\n", curr->fd);
//num_fds, the count of items in the array is set to 1
//because the listen socket is already present
num_fds = 1;
//This is the main loop.
//While (true)
// set all struct pollfd items revents to 0
// call poll
// loop through, see if there is data to read
// read the data
// loop through all sockets (except the listen_socket()) and send the data.
while (1)
{
//reset all event flag
for (i = 1; i < num_fds; i++)
{
curr = *(my_fds + i);
curr->events = POLLIN | POLLPRI;
printf("%i: fd %i\n", i, curr->fd);
curr->revents = 0;
send(curr->fd, "Enter some text:\n", 18, 0);
}
//put all this into poll and wait for something magical to happen
printf("calling poll (%d sockets)\n", num_fds);
if (poll(*my_fds, num_fds, TIMEOUT) == -1)
{
perror("poll");
exit(0);
}
printf("poll returned!\n");
//First item is the accepting socket....check it independently of the rest!
curr = *my_fds;
if (curr->revents != 0)
{
printf("We have a new connection.\nAccept goes here...\n");
//Accept the connection
sin_size = sizeof their_addr;
new_conn = (struct pollfd*) malloc(sizeof(struct pollfd));
new_conn->fd = accept(curr->fd, (struct sockaddr *)&their_addr, &sin_size);
new_conn->events = POLLIN;
new_conn->revents = 0;
printf("Connection from %s\n", inet_ntoa(their_addr.sin_addr));
sprintf(buff, "Your %i\n", num_fds);
send(new_conn->fd, buff, 7, 0);
//Add it to the poll call
*(my_fds + num_fds) = new_conn;
num_fds++;
}
else
{
//skip first one, we know that's the accepting socket (handled above).
for (i = 1; i < num_fds; i++)
{
curr = *(my_fds + i);
if (curr->revents != 0)
{
buff_sz = recv(curr->fd, &buff, 254, 0);
buff[buff_sz] = '\0';
printf("Recieved: %s", buff);
//send the message to everyone else
for (j = 1; j < num_fds; j++)
{
printf("i = %i, j = %i\n", i, j);
if (j != i)
{
new_conn = *(my_fds + j);
sprintf(buff2, "%i sent you %i: %s", i, j, buff);
send(new_conn->fd, buff2, strlen(buff2) + 1, 0);
}
}
}
}
}
}
printf("App Ended\n");
}
static int listen_socket()
{
struct sockaddr_in a;
int s;
int yes;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
return -1;
}
yes = 1;
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
(char *) &yes, sizeof(yes)) < 0) {
perror("setsockopt");
close(s);
return -1;
}
memset(&a, 0, sizeof(a));
a.sin_port = htons(PORT);
a.sin_family = AF_INET;
if (bind(s, (struct sockaddr *) &a, sizeof(a)) < 0) {
perror("bind");
close(s);
return -1;
}
printf("Accepting connections on port %d\n", PORT);
listen(s, 10);
return s;
}