Why is Connect() returning a negative value? - c

Question

#include<io.h>
#include<stdio.h>
#include<winsock2.h>
#include <ctype.h>
#include<string.h>
#include<strings.h>
#define MY_PORT 8989 //defining the port for the socket
#define MAXBUF 256
int main(int argc , char *argv[])
{
//char str[MAXBUF];
int a;
WSADATA wsa;
SOCKET sockfd , clientfd; //SOCKET is a data type. We initialize two variables of the data type Socket here
struct sockaddr_in self; //structure for the family,port and IP address of the socket (Socket descriptors)
char buffer[MAXBUF]; // this is a character array that will receive the message from the client and we will use this to manipulate
//char message[MAXBUF];
printf("\nInitialising Winsock...");
if (WSAStartup(MAKEWORD(2,2),&wsa) != 0) //WSASTARUP is used to tell windows to get ready for a connection and if it returns a value 0, windows is ready
{
printf("Failed. Error Code : %d",WSAGetLastError());
return 1;
}
printf("Initialised.\n");
/*---create streaming socket---*/
if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 ) //socket is created using a function called socket
//using AF_INET means that we are using TCP/IP family
//the if statement here checks whether or not the value returned by the socket is negative or not. If it is negative that means there is some sort of an error
{
perror("Socket");
exit(errno);
}
printf("Socket created.\n");
self.sin_family = AF_INET;
self.sin_port = htons(MY_PORT);
self.sin_addr.s_addr = htonl(INADDR_ANY);
memset(&self,'\0', sizeof(self));
/*The connect function below is used to establish a connection between the client and the server*/
if (connect(sockfd, (struct sockaddr*)&self, sizeof(self)) <0)
{
printf("connection with the server failed...\n");
exit(0);
}
else
printf("connected to the server..\n");
printf("Please enter message: ");
memset(buffer, 0, sizeof (buffer));
fgets(buffer, MAXBUF, stdin); //fgets is used here to get whatever is inside the buffer
while (1)
{
/*struct sockaddr_in client_addr;
int addrlen=sizeof(client_addr);*/
/*---accept a connection (creating a data pipe)---*/
a= write(sockfd, buffer, sizeof(buffer));
if(a<0){
printf("Error");
}
// a= recv(clientfd, buffer, MAXBUF, 0);
//accept(clientfd, (struct sockaddr*)&client_addr, &addrlen);
a= read(sockfd, buffer, sizeof(buffer));
if(a<0){
printf("Error");
}
if (strncmp("QUIT", buffer, 4) == 0) {
printf("Server Exit...\n");
break;
}
}
close(sockfd); //close the sockfd
WSACleanup(); // windows socket is cleaned up
return 0;
}
The code works completely fine but for some reason, which I can't wrap my head around the connect function keeps on returning a negative value, or at least a value that is not zero. The server I am using with this client works for other clients, so I know for a fact that there is nothing wrong with it.
Your help will be much appreciated.

Answer 1

self.sin_family = AF_INET;
self.sin_port = htons(MY_PORT);
self.sin_addr.s_addr = htonl(INADDR_ANY);
memset(&self,'\0', sizeof(self));
In this code you set all the values of self and then you just clear self with memset. I'm pretty sure that this makes no sense and likely is the cause of the error you see, i.e. no useful parameters given for connect.
Even without this erroneous memset the code does not make much sense: you are trying to connect to INADDR_ANY but there is no such IP address to connect to. INADDR_ANY means on the server side to listen on every address of the machine - on the client side it cannot be used but instead the real IP address have to be used, like 127.0.0.1 for localhost.