C socket programming: select() is returning 0 despite messages sent from server
- by Fantastic Fourier
Hey all, I'm using select() to recv() messages from server, using TCP/IP. When I send() messages from the server, it returns a reasonable number of bytes, saying it's sent successful. And it does get to the client successfully when I use while loop to just recv(). Everything is fine and dandy.
while(1)
recv() // obviously pseudocode
However, when I try to use select(), select() returns 0 from timeout (which is set to 1 second) and for the life of me I cannot figure out why it doesn't see the messages sent from the server. I should also mention that when the server disconnects, select() doesn't see that either, where as if I were to use recv(), it would return 0 to indicate that the connection using the socket has been closed. Any inputs or thoughts are deeply appreciated.
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#define SERVER_PORT 10000
#define MAX_CONNECTION 20
#define MAX_MSG 50
struct client
{
char c_name[MAX_MSG];
char g_name[MAX_MSG];
int csock;
int host; // 0 = not host of a multicast group
struct sockaddr_in client_address;
struct client * next_host;
struct client * next_client;
};
struct fd_info
{
char c_name[MAX_MSG];
int socks_inuse[MAX_CONNECTION];
int sock_fd, max_fd;
int exit;
struct client * c_sys;
struct sockaddr_in c_address[MAX_CONNECTION];
struct sockaddr_in server_address;
struct sockaddr_in client_address;
fd_set read_set;
};
struct message
{
char c_name[MAX_MSG];
char g_name[MAX_MSG];
char _command[3][MAX_MSG];
char _payload[MAX_MSG];
struct sockaddr_in client_address;
struct client peer;
};
int main(int argc, char * argv[])
{
char * host;
char * temp;
int i, sockfd;
int msg_len, rv, ready;
int connection, management, socketread;
int sockfds[MAX_CONNECTION];
// for three threads that handle new connections, user inputs and select() for sockets
pthread_t connection_handler, manager, socket_reader;
struct sockaddr_in server_address, client_address;
struct hostent * hserver, cserver;
struct timeval timeout;
struct message msg;
struct fd_info info;
info.exit = 0; // exit information: if exit = 1, threads quit
info.c_sys = NULL;
// looking up from the host database
if (argc == 3)
{
host = argv[1]; // server address
strncpy(info.c_name, argv[2], strlen(argv[2])); // client name
}
else
{
printf("plz read the manual, kthxbai\n");
exit(1);
}
printf("host is %s and hp is %p\n", host, hserver);
hserver = gethostbyname(host);
if (hserver)
{
printf("host found: %s\n", hserver->h_name );
}
else
{
printf("host not found\n");
exit(1);
}
// setting up address and port structure information on serverside
bzero((char * ) &server_address, sizeof(server_address)); // copy zeroes into string
server_address.sin_family = AF_INET;
memcpy(&server_address.sin_addr, hserver->h_addr, hserver->h_length);
server_address.sin_port = htons(SERVER_PORT);
bzero((char * ) &client_address, sizeof(client_address)); // copy zeroes into string
client_address.sin_family = AF_INET;
client_address.sin_addr.s_addr = htonl(INADDR_ANY);
client_address.sin_port = htons(SERVER_PORT);
// opening up socket
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
exit(1);
else
{
printf("socket is opened: %i \n", sockfd);
info.sock_fd = sockfd;
}
// sets up time out option for the bound socket
timeout.tv_sec = 1; // seconds
timeout.tv_usec = 0; // micro seconds ( 0.5 seconds)
setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timeval));
// binding socket to a port
rv = bind(sockfd, (struct sockaddr *) &client_address, sizeof(client_address));
if (rv < 0)
{
printf("MAIN: ERROR bind() %i: %s\n", errno, strerror(errno));
exit(1);
}
else
printf("socket is bound\n");
printf("MAIN: %li \n", client_address.sin_addr.s_addr);
// connecting
rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address));
info.server_address = server_address;
info.client_address = client_address;
info.sock_fd = sockfd;
info.max_fd = sockfd;
printf("rv = %i\n", rv);
if (rv < 0)
{
printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno));
exit(1);
}
else
printf("connected\n");
fd_set readset;
FD_ZERO(&readset);
FD_ZERO(&info.read_set);
FD_SET(info.sock_fd, &info.read_set);
while(1)
{
readset = info.read_set;
printf("MAIN: %i \n", readset);
ready = select((info.max_fd)+1, &readset, NULL, NULL, &timeout);
if(ready == -1)
{
sleep(2);
printf("TEST: MAIN: ready = -1. %s \n", strerror(errno));
}
else if (ready == 0)
{
sleep(2);
printf("TEST: MAIN: ready = 0. %s \n", strerror(errno));
}
else if (ready > 0)
{
printf("TEST: MAIN: ready = %i. %s at socket %i \n", ready, strerror(errno), i);
for(i = 0; i < ((info.max_fd)+1); i++)
{
if(FD_ISSET(i, &readset))
{
rv = recv(sockfd, &msg, 500, 0);
if(rv < 0)
continue;
else if(rv > 0)
printf("MAIN: TEST: %s %s \n", msg._command[0], msg._payload);
else if (rv == 0)
{
sleep(3);
printf("MAIN: TEST: SOCKET CLOSEDDDDDD \n");
}
FD_CLR(i, &readset);
}
}
}
info.read_set = readset;
}
// close connection
close(sockfd);
printf("socket closed. BYE! \n");
return(0);
}
