CPP/Sockets

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(Taken from here with non-trivial modifications: http://www.linuxhowtos.org/C_C++/socket.htm)

First run

server 51717

Then run (while 'server' is still running):

client localhost 51717

The client will ask you to type a message. Do this, and press enter. You will see the message appear in the server window!

client.cpp

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <cstdlib>
#include <cstring> // includes bzero
#include <fstream>
#include <iostream>
 
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)
    {
        std::cout << "ERROR opening socket" << std::endl;
        exit(-1);
    }
    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,(sockaddr*)(&serv_addr),sizeof(serv_addr)) < 0)
    {
        std::cout << "ERROR connecting" << std::endl;
        exit(-1);
    }
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n = write(sockfd,buffer,strlen(buffer));
    if (n < 0)
    {
         std::cout << "ERROR writing to socket" << std::endl;
         exit(-1);
    }
    bzero(buffer,256);
    n = read(sockfd,buffer,255);
    if (n < 0)
    {
         std::cout << "ERROR reading from socket" << std::endl;
    }
    printf("%s\n",buffer);
    return 0;
}

server.cpp

/* A simple server in the internet domain using TCP
   The port number is passed as an argument */
#include <stdio.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <cstdlib>
#include <cstring> // includes bzero
#include <iterator>
#include <iostream>
 
int main(int argc, char *argv[])
{
     int sockfd, newsockfd, portno, 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)
     {
        std::cout << "ERROR opening socket" << std::endl;
        exit(-1);
     }
     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)
     {
       std::cout << "ERROR on binding" << std::endl;
       exit(-1);
     }
     listen(sockfd,5);
     clilen = sizeof(cli_addr);
     newsockfd = accept(sockfd, 
                 (struct sockaddr *) &cli_addr, 
                 (socklen_t*)(&clilen));
     if (newsockfd < 0)
     {
          std::cout << "ERROR on accept" << std::endl;
          exit(-1);
     }
     bzero(buffer,256);
     n = read(newsockfd,buffer,255);
     if (n < 0)
     {
       std::cout << "ERROR reading from socket" << std::endl;
       exit(-1);
     }
     printf("Here is the message: %s\n",buffer);
     n = write(newsockfd,"I got your message",18);
     if (n < 0)
     {
       std::cout << "ERROR writing to socket" << std::endl;
       exit(-1);
     }
     return 0; 
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
 
Project(Sockets)
 
ADD_EXECUTABLE(server server.cpp)
ADD_EXECUTABLE(client client.cpp)