Sending to client from server [closed] - c

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I'm trying to send data from a server to a client whenever the client executes a recv() command. As the code stands right now, I cannot get the client to print any data it receives. I cannot figure out whether something is wrong with my server or client, so any help would be appreciated. Thanks!
client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#define ECHO_PORT 9999
#define BUF_SIZE 4096
int main(int argc, char* argv[])
{
if (argc != 3)
{
fprintf(stderr, "usage: %s <server-ip> <port>",argv[0]);
return EXIT_FAILURE;
}
char buf[BUF_SIZE];
int status, sock, sock2;
struct addrinfo hints;
memset(&hints, 0, sizeof(struct addrinfo));
struct addrinfo *servinfo; //will point to the results
hints.ai_family = AF_INET; //IPv4
hints.ai_socktype = SOCK_STREAM; //TCP stream sockets
hints.ai_flags = AI_PASSIVE; //fill in my IP for me
if ((status = getaddrinfo(argv[1], argv[2], &hints, &servinfo)) != 0)
{
fprintf(stderr, "getaddrinfo error: %s \n", gai_strerror(status));
return EXIT_FAILURE;
}
if ((sock = socket(servinfo->ai_family, servinfo->ai_socktype, servinfo->ai_protocol)) == -1)
{
fprintf(stderr, "Socket failed");
return EXIT_FAILURE;
}
if ((connect(sock, (struct sockaddr *) servinfo->ai_addr, servinfo->ai_addrlen)) != 0)
{
fprintf(stderr, "Connection failed");
return EXIT_FAILURE;
}
if ((sock2 = socket(servinfo->ai_family, servinfo->ai_socktype, servinfo->ai_protocol)) == -1)
{
fprintf(stderr, "Socket failed");
return EXIT_FAILURE;
}
if ((connect(sock2, (struct sockaddr *) servinfo->ai_addr, servinfo->ai_addrlen)) != 0)
{
fprintf(stderr, "Connection failed");
return EXIT_FAILURE;
}
while (1) {
//char msg[BUF_SIZE] = "ashudfshuhafhu";
//char msg[BUF_SIZE];
//fgets(msg, BUF_SIZE, stdin);
//int i = 2;
//if (strlen(msg) == i)
// break;
int bytes_received;
// fprintf(stdout, "Sending %s", msg);
//send(sock, msg , strlen(msg), 0);
if((bytes_received = recv(sock, buf, BUF_SIZE, 0)) > 1)
{
buf[bytes_received] = '\0';
fprintf(stdout, "Received %s", buf);
}
}
freeaddrinfo(servinfo);
close(sock);
return EXIT_SUCCESS;
}
Server.c
#include <netinet/in.h>
#include <netinet/ip.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#define ECHO_PORT 9999
#define BUF_SIZE 4096
int close_socket(int sock)
{
if (close(sock))
{
fprintf(stderr, "Failed closing socket.\n");
return 1;
}
return 0;
}
int main(int argc, char* argv[])
{
int sock, client_sock;
ssize_t readret;
socklen_t cli_size;
struct timeval tv;
struct sockaddr_in addr, cli_addr;
char buf[BUF_SIZE] = "wetwetwetwetwetwetwetwet";
fd_set readfds, writefds;
fd_set activereadfds, activewritefds;
cli_size = sizeof(&cli_addr);
tv.tv_sec = 5;
tv.tv_usec = 0;
fprintf(stdout, "----- Echo Server -----\n");
/* all networked programs must create a socket */
if ((sock = socket(PF_INET, SOCK_STREAM, 0)) == -1)
{
fprintf(stderr, "Failed creating socket.\n");
return EXIT_FAILURE;
}
addr.sin_family = AF_INET;
addr.sin_port = htons(ECHO_PORT);
addr.sin_addr.s_addr = INADDR_ANY;
/* servers bind sockets to ports---notify the OS they accept connections */
if (bind(sock, (struct sockaddr *) &addr, sizeof(addr)))
{
close_socket(sock);
fprintf(stderr, "Failed binding socket.\n");
return EXIT_FAILURE;
}
if (listen(sock, 5))
{
close_socket(sock);
fprintf(stderr, "Error listening on socket.\n");
return EXIT_FAILURE;
}
FD_ZERO(&readfds);
FD_SET(sock, &activereadfds);
while (1)
{
fprintf(stdout,"in here.\n");
readfds = activereadfds;
writefds = activewritefds;
FD_ZERO(&activereadfds);
FD_ZERO(&activewritefds);
if (select(51, &readfds, &writefds, NULL, &tv) < 0)
{
perror("select");
return EXIT_FAILURE;
}
for (int i = 0; i < 10; ++i)
{
if (FD_ISSET (i, &readfds))
{
if (i == sock)
{
fprintf(stdout, "main loop. \n");
client_sock = accept(sock,
(struct sockaddr *) &cli_addr, &cli_size);
FD_SET(client_sock, &activereadfds);
FD_SET(client_sock, &activewritefds);
if (client_sock < 0)
{
perror("accept");
return EXIT_FAILURE;
}
} else {
fprintf(stdout, "second loop \n");
readret = send(i,buf, strlen(buf),0);
if (readret < 0)
fprintf(stdout, "yay");
}
}
if (FD_ISSET(i, &writefds))
{ fprintf(stdout, "ugh \n");
readret = send(i,buf,BUF_SIZE,0);
//if (readret > 0)
//while((readret = recv(i, buf, BUF_SIZE, 0)) >= 1)
// {
//if (send(i, buf, readret, 0) != readret)
//{
// close_socket(i);
// close_socket(sock);
// fprintf(stderr, "Error sending to client.\n");
// return EXIT_FAILURE;
//}
}
}
}
close_socket(sock);
return EXIT_SUCCESS;
}

Answer 1

Your server is sending only when the socket is ready for reading, and as the client is never sending, the server isn't either. The server send should happen when the client socket turns up in the writefds, although actually this isn't the correct way to use that feature. Really you should just send, and only add into and worry about writefds if send() caused EAGAIN/EWOULDBLOCK.
You could be getting an undetected error in the client:
if((bytes_received = recv(sock, buf, BUF_SIZE, 0)) > 1)
{
buf[bytes_received] = '\0';
fprintf(stdout, "Received %s", buf);
}
This should continue:
else if (bytes_received == 0)
{
fprintf(stdout, "peer disconnected\n");
break;
}
else // < 0: error
{
fprintf(stdout, "recv() error %s\n", strerror(errno));
break;
}
You need to print the actual error like this whenever you get an error from a system call.