client/server

[nan20]

I want to do the TCP client/server communication between Raspberry Pi and laptop with Ubuntu OS running using VMware Workstation. Raspberry Pi act as the client and Ubuntu act as the server. I am able to successfully compile the client and server program.But on the client side it throws an error ERROR, no such host. I made changes in Ubuntu network settings to share with other computers. But still communication is not taking place. I am able to ping successfully between Raspberry Pi and Ubuntu. But I am not able to communicate between the client and server side. Can anyone solve this issue and suggest me how to do the network settings in Ubuntu so that Pi and Ubuntu can communicate.

client.c

Code: Select all

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

void error(const char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sockfd, portno, n;
    struct sockaddr_in serv_addr;
    struct hostent *server;

    char buffer[256];
    if (argc < 3) {
        fprintf(stderr,"usage %s hostname port\n", argv[0]);
        exit(0);
    }
    portno = atoi(argv[2]);
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) 
        error("ERROR opening socket");
    server = gethostbyname(argv[1]);
    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host\n");
        exit(0);
    }
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr, 
        (char *)&serv_addr.sin_addr.s_addr,
        server->h_length);
    serv_addr.sin_port = htons(portno);
    if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) 
        error("ERROR connecting");
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n = write(sockfd,buffer,strlen(buffer));
    if (n < 0) 
        error("ERROR writing to socket");
    bzero(buffer,256);
    n = read(sockfd,buffer,255);
    if (n < 0) 
        error("ERROR reading from socket");
    printf("%s\n",buffer);
    close(sockfd);
    return 0;
}


server.c

/* A simple server in the internet domain using TCP
   The port number is passed as an argument */
#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; 
}

[B.Goode]

Do you have a DNS server on your local network that is capable of resolving the hostname you enter into an IP address?

Or have you configured the hostname locally in /etc/hosts ?

(The underlying question is: how does the RPi find out the IP address of the server?)

[6by9]

You're doing well on using deprecated functions too:
bcopy is replaced by memcpy
bzero is replaced by memset
gethostbyname is replaced by getaddrinfo and getnameinfo

B.Goode is probably right though - how are you converting from a hostname to IP address? Does it work if you put the IP address of the Ubuntu box in as your hostname so no DNS lookup is required?