Comunicación vía sockets: ejecución

Clase 36 de 37 • Curso de Introducción a C 2019

Sebastian Andree Lopera Quevedo

student•

luche un poco para ver algunos errores, no me compilaba. Al final vi lo que mis compañeros dejaron y vi la logica de mi código porque el error no era de sintaxis. Gracias a mis compañeros de curso logre ver que me faltaron paréntesis por algun lado jaja tengan cuidado. Les dejo mi código por si quieren comparar si tienen problemas:

SERVIDOR

//libraries with the needed definitions:
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/*
struct sockaddr_in
{
  short int sin_family;
  unsigned short int sin_port;
  struct in_addr sin_addr;
  unsigned char sin_zero[8];
};

struct sockaddr
{
  unsigned short sa_family;
  char sa_data[14];
};

int socket(int domain, int type, int protocol);

int bind(int sockfd, const struct sockaddr *myaddr, int addrlen);

int listen(int s, int backlog);

int accept(int sockfd, const struct sockaddr *addr, socklen_t addrlen);

ssize_t send(int sockfd, const void *buf, size_t len, int flags);

ssize_t recv(int sockfd,       void *buf, size_t len, int flags);

int shotdown();
*/

#include <string.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char const *argv[])
{
  //the first argument will be the port of communication
  if (argc > 1)
  {
    //the needed variables
    int server_socket, client_socket, longitud_cliente, port;

    //casting the argument to an integer
    port = atoi(argv[1]);

    //defining the n-points
    struct sockaddr_in server;
    struct sockaddr_in client;

    // server variables
    server.sin_family = AF_INET;//protocol type (TCP-IP)
    server.sin_port = htons(port);//the integer with the port number gets transformed to the needed structure
    server.sin_addr.s_addr = INADDR_ANY;//any client could get connected
    bzero(&(server.sin_zero), 8);//this function fulls a string with 0's

    if ((server_socket = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    //a socket is created for the server (protocol family, specific protocol (TCP/IP), configuration (0 for automatic configuration))
    //if the function goes right returns a value different of -1
    {
      printf("no pude abrir el socket\n");//printed in case of opening error

      return 1;
    }
    if (bind(server_socket, (struct sockaddr *) &server, sizeof(struct sockaddr)) == -1)
    //the server socket is associated to a port (the scoket, a pointer to a socket address structure for the configuration, size of the structure)
    //if the function goes right returns a value different of -1
    {
      printf("no pude abrir el puerto %s y asociarlo con el socket\n", argv[1]);//this could happen if the port is already opened by other application

      return 2;
    }

    if (listen(server_socket, 5) == -1)
    //the port now is listening for only 5 clients
    //if the function goes right returns a value different of -1
    {
      printf("no pude ponerme en modo escucha\n");

      return 3;
    }

    //accepting clients
    printf("Todo listo! Aceptando clientes...\n");
    longitud_cliente = sizeof(struct sockaddr_in);
    if ((client_socket = accept(server_socket, (struct sockaddr *) &client, &longitud_cliente)) == -1)
    //accepts the first client waiting for service (the server_socket accepts the conection, a pointer to a socket address structure for the configuration, size of the structure)
    //if the function goes right returns a value different of -1
    {
      printf("No se pudo establecer conección con \n");

      return 4;
    }

    //at this point the conection has been established

    //in order to see the client's direction...
    char str[INET_ADDRSTRLEN];
    //...transforms a direction to a string (protocol, direction to trasform, pointer to a buffer where the address is going to be saved, max size of the buffer)
    inet_ntop(AF_INET, &(client.sin_addr), str, INET_ADDRSTRLEN);

    //it advice the client connected, his IP and port
    printf("Se conectó un cliente desde la IP: %s, desde el puerto: %d\tlo saludo\n", str, port);

    //send a message to the client (to who, message, size of the message, modificators bit to bit (0 for no one))
    send(client_socket, "Bienvenido a mi pedilecto, sublime y elegante servidor.", 55, 0);

    //advice that the graet has been sent
    printf("Saludo enviado!\n");

    //closing the communication(closing socket, how it gonna be closed (2 for be closed completly))
    shutdown(client_socket, 2);
    shutdown(server_socket, 2);
  }
  else
  //if the port has not been passed by the command parameter
  {
    printf("No se indicó el puerto\n");

    return 5;
  }

  return 0;
}

CLIENTE

//libraries with the needed definitions:
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/*
struct sockaddr_in
{
  short int sin_family;
  unsigned short int sin_port;
  struct in_addr sin_addr;
  unsigned char sin_zero[8];
};

struct sockaddr
{
  unsigned short sa_family;
  char sa_data[14];
};

int socket(int domain, int type, int protocol);

int bind(int sockfd, const struct sockaddr *myaddr, int addrlen);

int listen(int s, int backlog);

int accept(int sockfd, const struct sockaddr *addr, socklen_t addrlen);

ssize_t send(int sockfd, const void *buf, size_t len, int flags);

ssize_t recv(int sockfd,       void *buf, size_t len, int flags);

int shotdown();
*/

#include <string.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char const *argv[])
{
  //the first argument will be the server IP
  //the second argument will be the communication port
  if (argc > 2)
  {
    //a string that holds the server IP
    const char *ip;
    //a socket for the client, the amount of bytes that will be recieved or sent, the port
    int client_socket, numbytes, port;

    char buff[100];//pff it's a buffer

    //giving the respective values to the IP and port
    ip = argv[1];
    port = atoi(argv[2]);
    //server information
    struct sockaddr_in server;

    if (inet_pton(AF_INET, ip, &server.sin_addr) <= 0)
    //convert the argument to an IP address (protocol family, specific protocol (TCP/IP), configuration (0 for automatic configuration))
    ////if the function goes right returns a value different of -1
    {
      printf("la IP %s no es valida\n", ip);

      return 1;
    }

    //creating the client socket
    printf("Abriendo el socket del cliente...\n");
    if ((client_socket = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    //a socket is created for the client (protocol family, specific protocol (TCP/IP), configuration (0 for automatic configuration))
    //if the function goes right returns a value different of -1
    {
      printf("no pude abrir el socket\n");

      return 2;
    }

    //server variables to especify which server to connect to
    server.sin_family = AF_INET;//protocol type (TCP-IP)
    server.sin_port = htons(port);//the integer with the port number gets transformed to the needed structure
    bzero(&(server.sin_zero), 8);//this function fulls a string with 0's

    //trying to get connected
    printf("Conectando a IP: %s, desde el puerto: %d\n", ip, port);
    if (connect(client_socket, (struct sockaddr *) &server, sizeof(struct sockaddr)) == -1)
    //the client socket is connecting to a server (the scoket, a pointer to a socket address structure for the configuration, size of the structure)
    //if the function goes right returns a value different of -1
    {
      printf("no pude conectarme al servidor\n");

      return 3;
    }

    //recieving message and printing it
    printf("Recibiendo...\n");////////////////
    if ((numbytes = recv(client_socket, buff, 100, 0)) == -1)
    //recieve a message from the server (///////////to who, a pointer to the buffer where the message is gonna be saved, size of the buffer, modificators bit to bit (0 for no one))
    //if the function goes right returns a value different of -1
    {
      printf("no se recibio el mensaje\n");

      return 4;
    }
    buff[numbytes] = '\0';
    printf("El servidor envia:\t'%s'\n", buff);

    //closing the communication(closing socket, how it gonna be closed (2 for be closed completly))
    shutdown(client_socket, 2);
  }
  else
  //if the port has not been passed by the command parameter
  {
    printf("No se indico la IP o el puerto\n");

    return 5;
  }

  return 0;
}```


Todo está bastante bien comentado en inglés asi que espero les sirva.

Comunicación vía sockets: ejecución

Comprender qué es el lenguaje C

¿Dónde aprender C?

Introducción al curso

Herramientas para programar en C

Aprender los conceptos iniciales del lenguaje C

Compilación y ejecución de un programa en C

Tipos de datos

Definición de variables

Control de flujos

Uso y definición de funciones

Directivas de pre-compilador

Conceptos esenciales

Entender conceptos más profundos del lenguaje C

Punteros

Usos prácticos de los punteros

Aritmética de punteros

Arreglos

Strings

Strings y memoria

Parámetros de línea de comandos

Definición de tipos de datos estructurados

Alias de tipos de datos

Crear bibliotecas propias

Comprender los desafìos de la administración de la memoria

Manejo dinámico de la memoria

Cómo instalar Valgrind

Memory leaks y Garbage Collectors

Listas enlazadas

Ejercicio práctico de listas enlazadas

Liberando las listas enlazadas

Reto: Modifica el programa para que permita eliminar los nodos en los que se encuentre un determinado número

Usos prácticos

Cálculos complejos

Manejo de archivos de texto

Manejo de archivos binarios

Paralelismo

Comunicación entre procesos

Pipes

Sockets

Sockets: Código del servidor

Sockets: código de cliente

Comunicación vía sockets: ejecución

Conclusiones

Conclusiones