Can anyone please help to make server.c for non-blocking I/O for TCP socket programming?

cola · 04-11-2024, 10:47 AM

Can anyone please help to make server.c for non-blocking I/O for TCP socket programming? I am trying to make multiple clients to connect to this server. I have tried the following code:

Code:

#include <stdio.h> 
#include <netdb.h> 
#include <netinet/in.h> 
#include <stdlib.h> 
#include <string.h> 
#include <sys/socket.h> 
#include <sys/types.h> 
#include <unistd.h> // read(), write(), close()
#include <arpa/inet.h>
#include <fcntl.h>
#define MAX 80 
#define PORT 8080 
#define SA struct sockaddr 

void func(int connfd) 
{ 
	char buff[MAX]; 
	int n; 
	// infinite loop for chat 
	for (;;) { 
		bzero(buff, MAX); 

		// read the message from client and copy it in buffer 
		read(connfd, buff, sizeof(buff)); 
		// print buffer which contains the client contents 
		printf("From client: %s\t To client : ", buff); 
		bzero(buff, MAX); 
		n = 0; 
		// copy server message in the buffer 
		while ((buff[n++] = getchar()) != '\n') 
			; 

		// and send that buffer to client 
		write(connfd, buff, sizeof(buff)); 

		// if msg contains "Exit" then server exit and chat ended. 
		if (strncmp("exit", buff, 4) == 0) { 
			printf("Server Exit...\n"); 
			break; 
		} 
	} 
} 

// Driver function 
int main() 
{ 
	int sockfd, connfd;
    socklen_t len; 
	struct sockaddr_in servaddr, cli; 

	// socket create and verification 
	sockfd = socket(AF_INET, SOCK_STREAM, 0); 
	if (sockfd == -1) { 
		printf("socket creation failed...\n"); 
		exit(0); 
	} 
	else
		printf("Socket successfully created..\n");
	
	
	int flags = fcntl(sockfd, F_GETFL, 0);
 	flags |= O_NONBLOCK;
 	int status = fcntl(sockfd, F_SETFL, flags);
	//printf("status: %d\n", status);

	bzero(&servaddr, sizeof(servaddr)); 

	// assign IP, PORT 
	servaddr.sin_family = AF_INET; 
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY); 
    //servaddr.sin_addr.s_addr = inet_addr("192.168.1.103"); 
	servaddr.sin_port = htons(PORT); 

	// Binding newly created socket to given IP and verification 
	if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) { 
		printf("socket bind failed...\n"); 
		exit(0); 
	} 
	else
		printf("Socket successfully binded..\n"); 

	// Now server is ready to listen and verification 
	if ((listen(sockfd, 5)) != 0) { 
		printf("Listen failed...\n"); 
		exit(0); 
	} 
	else
		printf("Server listening..\n"); 
	len = sizeof(cli); 

	while(1) {
		// Accept the data packet from client and verification 
		connfd = accept(sockfd, (SA*)&cli, &len); 
		if (connfd < 0) { 
			printf("server accept failed...\n"); 
			exit(0); 
		} 
		else
			printf("server accept the client...\n"); 

		// Function for chatting between client and server 
		func(connfd); 
	}
	close(sockfd); 
}

I have got the output like this:

Code:

Socket successfully created..
Socket successfully binded..
Server listening..
server accept failed...

NevemTeve · 04-11-2024, 11:02 AM

Print `errno` and `strerror(errno)`.

teckk · 04-11-2024, 04:01 PM

The best I can tell you need to change this...,

Code:

connfd = accept(sockfd, (SA*)&cli, &len);

Instead of me trying to rewrite this, here, a working example, you rewrite it.

Code:

//gcc BindPort.c -o BindPort

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

void error(const char *msg) {
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[])
{
    int sockfd, newsockfd, portno;
    socklen_t clilen;
    char buffer[256];
    struct sockaddr_in serv_addr, cli_addr;
    int n;
    
    if (argc < 2) {
        fprintf(stderr,"ERROR, no port provided\n");
        exit(1);
    }
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    
    if (sockfd < 0)
        error("ERROR opening socket");
        
    bzero((char *) &serv_addr, sizeof(serv_addr));
    portno = atoi(argv[1]);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(portno);
    
    if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
        error("ERROR on binding");
        
    listen(sockfd,5);
    clilen = sizeof(cli_addr);
    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
    
    if (newsockfd < 0)
        error("ERROR on accept");
        
    bzero(buffer,256);
    n = read(newsockfd,buffer,255);
    
    if (n < 0) 
        error("ERROR reading from socket");
        
    printf("Here is the message: %s\n",buffer);
    n = write(newsockfd,"I got your message",18);
    
    if (n < 0) error("ERROR writing to socket");
        close(newsockfd);
        
    close(sockfd);
    return 0;
}

Compiled, ran executable, Opened a web browser to http://127.0.0.1:8100/

Code:

gcc BindPort.c -o BindPort

./BindPort 8100

Here is the message: GET / HTTP/1.1
Host: 127.0.0.1:8100
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/123.0.6312.52 Mobile/15E148 Safari/604.1