Question

The server has to echo the message sent by the client using C program in Linux.I’m using Ubuntu OS (I don’t know whether this information is useful or not!). It worked for the first time. But for the second time, it gave ‘Error Connection’. I tried changing port numbers. But still it didn’t work. Kindly guide me. I’m a beginner.

server.c

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

int main()
{
    int sd, sd1, len, confd, n;
    struct sockaddr_in ser, cli;
    char msg[50];

    if((sd = socket(AF_INET,SOCK_STREAM, 0)) < 0)
        printf("\nSocket creation error\n");

    bzero(&ser, sizeof(ser));
    ser.sin_family = cli.sin_family = PF_INET;
    ser.sin_port = htons(10000);
    ser.sin_addr.s_addr = htonl(INADDR_ANY);
    len = sizeof(ser);

    if ((bind(sd, (struct sockaddr*)&ser, len)) < 0) {
        printf("\nBind Error");
        exit(0);
    }
    if (listen(sd, 2) == 0) {
        if ((sd1 = accept(sd, (struct sockaddr*)&ser, &len)) > 0) {
            do {
                bzero(&msg, 50);
                read(sd1, msg, 50);
                //int m=(int)msg;
                printf("\nMessage from client:%s\n", msg);
                write(sd1, msg, strlen(msg));
                if(strcmp(msg, "exit") == 0)
                    break;
            } while(strcmp(msg, "exit") != 0);
        }
    }
}

*strong text*client.c

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

int main()
{
    int sd, n, len;
    struct sockaddr_in ser, cli;
    char text[50];

    if ((sd = socket(AF_INET,SOCK_STREAM, 0)) < 0)
        printf("\nSocket creation error\n");

    bzero(&ser, sizeof(ser));
    ser.sin_family = cli.sin_family = PF_INET;
    ser.sin_port = htons(10000);
    ser.sin_addr.s_addr = htonl(INADDR_ANY);
    len = sizeof(ser);

    if ((connect(sd, (struct sockaddr*)&ser, len)) < 0) {
        printf("\nError connection");
        exit(0);
    }
    while(1) {
        strcpy(text, " ");
        printf("\nEnter data which is to be sent:");
        scanf("%s", text);
        write(sd, text, strlen(text));
        read(sd, text, 50);
        printf("\nEcho msg from server:%s", text);
        if (strcmp(text, "exit") == 0)
            break;
    }
    close(sd);
}

Answer 1

Can your client really connect to any address?

ser.sin_addr.s_addr=htonl(INADDR_ANY);

Most likely you meant to connect to a specific server:

ser.sin_addr.s_addr=inet_addr("127.0.0.1");