Thread: c++ sockets

Hi, I am trying to write a simple echo server as I have just started using sockets in c++. I am using beej's guide, which was written for c but I was told that the functions are the same in c++. However I get the following error when I try to compile the server program.

Code:

server.cpp: In function ‘int main()’:
server.cpp:34: error: expected initializer before ‘struct’
server.cpp:43: error: ‘server_addr’ was not declared in this scope
server.cpp:53: error: ‘list_check’ was not declared in this scope
server.cpp:59: error: ‘sin_size’ was not declared in this scope
server.cpp:63: error: comparison between distinct pointer types ‘std::string*’ and ‘const char*’ lacks a cast

I understand what I am doing wrong for the last error and I will fix that, wanted to try and see if I could just use strings as I find them easier to work with.

Code:

#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string>

using namespace std;

int main()
{
        struct sockaddr_in
        {
                short int          sin_family;  // Address family
                unsigned short int sin_port;    // Port number
                struct in_addr     sin_addr;    // Internet address
                unsigned char      sin_zero[8]; // Same size as struct sockaddr
        };

        int sockfd, clientsock;
        //int len1, len2, len3;

        string *buf;

        int bind_check, list_check //variables used in error checking

        //char *msg1 = "Connected to server...";
        //char *msg2 = "Initializing data transfer...";
        //char *msg3 = "Ready. Commence data transfer.";
        //len1 = strlen(msg1);
        //len2 = strlen(msg2);
        //len3 = strlen(msg3);

        struct sockaddr_in server_addr;
        struct sockaddr_in client_addr;
        sockfd=socket(PF_INET, SOCK_STREAM, 0 );
        if ( sockfd == -1 )
        {
                cout<<"Could not bind socket.\n";
                return 1;
        }

        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(31337);
        server_addr.sin_addr.s_addr = INADDR_ANY;
        memset(server_addr.sin_zero, '\0', sizeof server_addr.sin_zero);

        bind_check=bind( sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr) );
        if ( bind_check == -1 )
        {
                cout<<"Could not bind socket.\n";
        }
        list_check=listen( sockfd, 5 );
        if( list_check == -1 )
        {
                cout<<"Could not listen() on the socket"<<sockfd<<"\n";
        }

        sin_size = sizeof( struct sockaddr_in );

        clientsock=accept( sockfd, (struct sockaddr *)&client_addr, &sin_size );

        while ( buf != "exit" )
        {
                if ( recv( clientsock, buf, 500, 0 ) == 0 )
                {
                        cout<<"Remote host closed connection. Firewall?";
                }
        }
        close(sockfd);
        close(clientsock);
}

I have no idea what I am doing wrong, I'm still pretty new to c++, so any advice will be appreciated.

Why are you declaring struct sockaddr_in yourself? Don't do that.

ok, those were pretty stupid mistakes, should have seen them :P

I changed the source and there are only a few errors left:

Code:

server.cpp: In function ‘int main()’:
server.cpp:53: error: invalid conversion from ‘int*’ to ‘socklen_t*’
server.cpp:53: error:   initializing argument 3 of ‘int accept(int, sockaddr*, socklen_t*)’

Code:

#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string>

using namespace std;

int main()
{
        int sockfd, clientsock, sin_size;
        //int len1, len2, len3;

        char *buf;

        int bind_check, list_check; //variables used in error checking

        //char *msg1 = "Connected to server...";
        //char *msg2 = "Initializing data transfer...";
        //char *msg3 = "Ready. Commence data transfer.";
        //len1 = strlen(msg1);
        //len2 = strlen(msg2);
        //len3 = strlen(msg3);

        struct sockaddr_in server_addr;
        struct sockaddr_in client_addr;
        sockfd=socket(PF_INET, SOCK_STREAM, 0 );
        if ( sockfd == -1 )
        {
                cout<<"Could not bind socket.\n";
                return 1;
        }

        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(31337);
        server_addr.sin_addr.s_addr = INADDR_ANY;
        memset(server_addr.sin_zero, '\0', sizeof server_addr.sin_zero);

        bind_check=bind( sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr) );
        if ( bind_check == -1 )
        {
                cout<<"Could not bind socket.\n";
        }
        list_check=listen( sockfd, 5 );
        if( list_check == -1 )
        {
                cout<<"Could not listen() on the socket"<<sockfd<<"\n";
        }

        sin_size = sizeof( struct sockaddr_in );

        clientsock=accept( sockfd, (struct sockaddr *)&client_addr, &sin_size );

        while ( buf != "exit" )
        {
                if ( recv( clientsock, buf, 500, 0 ) == 0 )
                {
                        cout<<"Remote host closed connection. Firewall?";
                }
        }
        close(sockfd);
        close(clientsock);
}

Originally Posted by Calef13

Code:

server.cpp: In function ‘int main()’:
server.cpp:53: error: invalid conversion from ‘int*’ to ‘socklen_t*’

This error wouldn't have happened in C. C++ is pickier about types. Define sin_size as a socklen_t instead of a plain old int. The second error is probably due to the same problem.

That fixed it. Thanks a lot for your help everyone. It compiled, now all I need to do is write a client :P

Calef13

why this message comes to me?
server.cpp: In function ‘int main()’:

and was not declared in this scope as well

please help me by any hints .

Code:

#include <time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/types.h>      
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <pthread.h>
#include <iostream>
#include <arpa/inet.h>

using namespace std;

extern void *serve(void *);

int main(int argc, char *argv[])
{
  int port = htons(atoi(argv[1]));
  int ssock, connsock, s;
  
  struct sockaddr_in myaddr;
  ssock = socket(AF_INET, SOCK_STREAM, 0);
  myaddr.sin_family = AF_INET;
  myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  myaddr.sin_port = port;
  s=bind(ssock,(struct sockaddr *)&myaddr,sizeof(myaddr));
  if(s < 0)
    
    {
      cerr << "cant bind\n"; exit(1);
    }
  
  listen(ssock,5); 
  
  pthread_t th;
  int r;
  while(true)
    
    {
      connsock=accept(ssock,0,0);
      r=pthread_create(&th,0,serve,(void *)connsock);
    }
  
}

void *serve(void *s)
{
  int fin, fout, n;
  int sock = (int)s, rc;
  char buffer[2048],req[2048],resource[2048],protoc[2048],contentLengths[2048],dates[2048];  
  char fname[2048] ="pages/", logfile[2048], *exts, *hostip; 
  
  unsigned short port;
  unsigned int cliaddrlen;
  struct sockaddr_in myaddr, cliaddr;
  
  pthread_detach(pthread_self());  
  rc = read(sock,buffer,2048);
  
  n=sscanf(buffer,"%s %s %s", req, resource, protoc);
  
  const char *reply1="HTTP/1.1 501 Method Not Implemented\r\nConnection: Close\r\n\r\n<h1>sorry</h1>\r\n";
  const char *reply2="HTTP/1.1 200 OK\r\nConnection: Close\r\n";
  const char *reply3="HTTP/1.1 404 File Not Found\r\nConnection: Close\r\n\r\n<h1>sorry</h1>\r\n";
  
  const char *reply4="Content-Type: text/html\r\n\r\n";
  const char *reply5="Content-type: image/jpeg\r\n\r\n";
  const char *reply6="Content-type: text/plain\r\n\r\n";
  
  const char *reply8="New connection\r\n\r\n";
  const char *length="Content-Length: %d\r\n";  
  
  struct stat statbuf;
  struct tm tmbuf;
  time_t mtime;
  
  fout=open ("logfile",O_APPEND|O_WRONLY|O_CREAT,0644); 
  time(&mtime);
  
  hostip = inet_ntoa(cliaddr.sin_addr); 
  port = ntohs(cliaddr.sin_port);
  
  
  gmtime_r(&mtime, &tmbuf);//returns the time the connection was made and the type of request.
  sprintf(logfile,req,protoc ,2048 ,"---Connection time: %A, %d-%b-%y %T GMT\r\n",&tmbuf);
  
  write(fout, logfile, strlen(logfile));;
  close (fout);
  
  if(strcmp(req,"GET")==0) // depending on the request it prints out the correct protocol response
    {
      strcat(fname,resource+1);
      if(access(fname,F_OK) <0)
	{
	  write(sock,reply3,strlen(reply3));
	}
      else
	{ 
	  write(sock,reply2,strlen(reply2));
	  exts = strrchr(fname, '.');
	  
	  if(strcmp(exts,".cgi")==0)          
	    { 
	      int pid;
	      pid = fork();         
	      
	      if (fork == 0)
		{
		  dup2(sock,0);
		  dup2(sock,1);
		  
		  execlp(fname, fname,0);
		  exit(2); 
               	}
	    }
	  else 
	    {
	      
	      stat(fname,&statbuf);// shows the content-length of the file that been sent by the response.
	      sprintf(contentLengths,length,statbuf.st_size); 
	      write(sock,contentLengths,strlen(contentLengths));
	      
	      mtime = statbuf.st_mtime;//Shows the last modified time if the file exists.
	      gmtime_r(&mtime, &tmbuf);
	      strftime(dates,2048 ,"Last-Modified: %A, %d-%b-%y %T GMT\r\n",&tmbuf); 
              write(sock,dates,strlen(dates));
	      
	      // checks the extension of the name of the requested file eg. html.
	      if(strcmp(exts,"jpg")==0 || strcmp(exts,"jpeg")==0)
                {
		  write(sock,reply5,strlen(reply5));
		}
	      if (strcmp(exts, "txt")==0)
                {
                  write(sock,reply6,strlen(reply6));
                } 
	      else 
		{
		  write(sock,reply4,strlen(reply4));
		}
	      fin=open(fname,O_RDONLY);
	      
	      rc = read(fin, buffer, 2048);
	      while(rc > 0) 
		{
		  write(sock, buffer, rc);
		  rc = read(fin, buffer, 2048);
		}
	      close(fin);
	    }
        }
    }
  else 
    
    {
      write(sock,reply1,strlen(reply1));
    }
  close(sock);
  pthread_exit(0);
}