The following code is a programming sample for using UDP sockets.
There are 3 .c
source files (Client_UDP.c
, Server_UDP.c
, and Message_UDP.c
), and 1 .h
header file (Prototype.h
).
I want the Server and Client to communicate with each other only through the functions in Message_UDP
.
The course of events seems to be like this:
- The Client sends a first packet/message to the Server.
- The Server receives the packet from the Client.
- The Server tries to send a response package, but shows an error:
"Error in sendto(): Address family not supported by protocol"
.
Does anyone know why? How can I solve this?
Client_UDP.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "Prototype.h"
int main(int argc, char * argv[]) {
int fd_socket;
struct sockaddr_in server;
socklen_t length_server = sizeof (server);
fd_socket = socket(AF_INET, SOCK_DGRAM, 0);
Error_A(fd_socket, "Error in socket()");
server.sin_port = htons(8888);
server.sin_family = AF_INET;
server.sin_addr.s_addr = inet_addr("127.0.0.1");
// send packet to server
function_SEND(fd_socket, server, length_server, "CLIENT");
// receive packet from server
function_RECEIVE(fd_socket, server, length_server, "CLIENT");
close(fd_socket);
return EXIT_SUCCESS;
}
Server_UDP.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "Prototype.h"
int main(int argc, char * argv[]) {
int fd_socket;
int rv; // return value
struct sockaddr_in server;
struct sockaddr_in client;
socklen_t length_server = sizeof (server);
socklen_t length_client = sizeof (client);
fd_socket = socket(AF_INET, SOCK_DGRAM, 0);
Error_A(fd_socket, "Errore in socket()");
server.sin_port = htons(8888);
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
rv = bind(fd_socket, (struct sockaddr *) &server, length_server);
Error_A(rv, "Error in bind()");
// receive packet from client
function_RECEIVE(fd_socket, client, length_client, "SERVER");
// send packet to client
function_SEND(fd_socket, client, length_client, "SERVER");
close(fd_socket);
return EXIT_SUCCESS;
}
Message_UDP.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "Prototype.h"
void Error_A(int return_value, char *error_message) {
if (return_value < 0) {
perror(error_message);
exit(EXIT_FAILURE);
}
}
void function_SEND(int fd_socket, struct sockaddr_in host, int length_host, char *sender) {
int rv; // return value
char packet[100] = "PACKET";
// send packet
rv = sendto(fd_socket, packet, 100, 0, (struct sockaddr *) &host, length_host);
Error_A(rv, "Error in sendto()");
printf("<%s> -- package sent: <%s> \n", sender, packet);
}
void function_RECEIVE(int fd_socket, struct sockaddr_in host, int length_host, char* receiver) {
int rv; // return value
char packet[100] = "";
// receive packet
rv = recvfrom(fd_socket, packet, 100, 0, (struct sockaddr *) &host, &length_host);
Error_A(rv, "Errore in recvfrom()");
printf("<%s> -- packet received: <%s> \n", receiver, packet);
}
Prototype.h
void Error_A(int return_value, char *error_message);
void function_SEND(int fd_socket, struct sockaddr_in host, int length_host, char *sender);
void function_RECEIVE(int fd_socket, struct sockaddr_in host, int length_host, char* receiver);
This is the client output:
CLIENT -- package sent: PACKET
This is the server output:
SERVER -- package received: PACKET
Error in sendto(): Address family not supported by protocol
server.sin_port = htons(8888);
– Some programmer duderecvfrom
, and do some research about emulating pass by reference in C. – Some programmer dudeclient
can still be a structure object like now, but you should modify yourfunction_RECEIVE
to expect a pointer, and pass it like you pass the structure torecvfrom
. – Some programmer dude