udp server does not receive message from udp linux client

Question

Well, I was programming a simple messaging system,when I tested it on the same computer,it worked properly without any problems,but when I tested it on two different computers,?

client code

#include <stdio.h>
#include <stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>

#define SERVER "127.0.0.1"
#define BUFFTAM 1024  //Tamanho maximo do buffer
#define PORTA 8888   //A porta na qual sera enviado os dados

void terminar(char *s)
{
    perror(s);
    exit(1);
}

void IniciarCliente()
{
    struct sockaddr_in servidorsock;/*definindo as variaveis*/
    int s, slen=sizeof(servidorsock);
    char buf[BUFFTAM];
    char mensagem[BUFFTAM];

    if ( (s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
        terminar("socket");
    }

    memset((char *) &servidorsock, 0, sizeof(servidorsock));
    servidorsock.sin_family = AF_INET;
    servidorsock.sin_port = htons(PORTA);

    if (inet_aton(SERVER , &servidorsock.sin_addr) == 0)
    {
        fprintf(stderr, "inet_aton() failed\n");
        exit(1);
    }

    while(strcmp(buf,"fim\n")!=0){
        printf("Digite uma mensagem : ");
        fgets(mensagem,BUFFTAM,stdin);

        //Envia a mensagem
        if (sendto(s, mensagem, strlen(mensagem) , 0 , (struct sockaddr *) &servidorsock, slen)==-1){
            terminar("sendto()");
        }

        //recebe uma mensagem de volta e printa ela na tela
        //limpa o buffer de dados
        memset(buf,'\0', BUFFTAM);
        printf("pacote enviado com sucesso!");
        //tenta receber dados do servidor
        if (recvfrom(s, buf, BUFFTAM, 0, (struct sockaddr *) &servidorsock, (socklen_t *)&slen) == -1){
            terminar("recvfrom()");
        }
        printf("pacote recebido com sucesso!");
        //printa os dados recebidos
        printf("%s\n",buf);
    }

    close(s);
}

int main()
{
    IniciarCliente();
    return 0;
}

server code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#define BUFFTAM 1024
#define PORTA 8888

void terminar(char *s)
{
    perror(s);
    exit(1);
}

void IniciarServer(){
    struct sockaddr_in servidorsock, cliente;
    int s, slen = sizeof(cliente);

    char buf[BUFFTAM];

    //cria um scoket udp
    if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
        terminar("socket");
    }

    // zera a estrutura
    memset((char *) &servidorsock, 0, sizeof(servidorsock));

    servidorsock.sin_family = AF_INET;
    servidorsock.sin_port = htons(PORTA);
    servidorsock.sin_addr.s_addr = htonl(INADDR_ANY);

    //faz o bind do socket com a porta
    if( bind(s , (struct sockaddr*)&servidorsock, sizeof(servidorsock) ) == -1){
        terminar("bind");
    }

    //espera por dados
    while(strcmp(buf,"fim\n")!=0){
        printf("Esperando por dados\n");
        fflush(stdout);
        memset(buf,'\0',BUFFTAM);

        //tenta receber algum dado do cliente
        if (recvfrom(s, buf, BUFFTAM, 0, (struct sockaddr *) &cliente, (socklen_t*)&slen) == -1){
            terminar("recvfrom()");
        }

        //imprime os dados recebidos
        printf("Origem do cliente %s:%d\n", inet_ntoa(cliente.sin_addr), ntohs(cliente.sin_port));
        printf("mensagem: %s\n" , buf);

        printf("Digite a mensagem que deseja enviar ao cliente : ");
        fgets(buf,BUFFTAM,stdin);

        //retorna o cliente com a mensagem
        if (sendto(s, buf, strlen(buf), 0, (struct sockaddr*) &cliente, slen) == -1){
            terminar("sendto()");
        }
    }

}


int main()
{
    IniciarServer();
    return 0;
}

I don’t know exactly what it is,

Answer 1

I was able to solve the problem, for whoever has the same problem I have,:

If you are using two different machines to connect, you will need to go to your router settings and try to change the dynamic IP of your router-generated machine and make it a static IP on your network,then you can use this machine as a server,and any other machine as a client,.

Tip: try to find some program that does this(change the dynamic IP of a machine to a static IP), because making your machine’s ip as static by the router is a very laborious task

If you are using a virtual machine (VM or virtual machine), which was my case, the process becomes simpler, by selecting your VM you only need to configure your network at Filing cabinet->preferences->Network,and add the client’s ip and the server’s ip (which would be the VM) and type in the port on which you would last, settings and would configure the host-only option on your VM,: https://terminaldeinformacao.com/2013/10/29/criando-conexao-host-only-no-virtualbox/ ,remembering again that you will need to set the static IP of your server in the client code so that it is possible to make the connection