Socket Programming, step out of the neophyte stage. CPP version
One of the most important ascpects in programming is to be able to let your programms talk to, configure, or monitor networks. This can be used to test a servers conectivity on the fly, or set up a server on a target machine so you can connect to it remotely.
You will not always have access to a tool that someone else made. So my hopes with this tut is that you can learn to roll your own tools out on the fly. I will start these string of tuts out with a simple tcp client. This program will send an HTTP request to a server and listen for a response. This is a good way to quickly test the status of a server.
Read each line of code, and the comments should help explain what each line does. There will be a more detailed tut for this on Turorials page. This is also where I will post all following tutorials.
Lets get started:
NOTE: The Code following is for linux.
CPP code
#include <cstring>
#include <sys/socket.h> //Needed to create the socket. Gives access to system commands for sockets
#include <netdb.h> //Needed for socket
#include <unistd.h> //Since gcc 4.7 you now need this to close socket
using namespace std;
int main()
{
int connStatus; //Store the status for the server info population
struct addrinfo host_info; // The struct that getaddrinfo() uses
struct addrinfo *host_info_list; // Set up a list for different host infos
//0 fill the struct. Make sure there is no bad data
memset(&host_info, , sizeof host_info);
//Set up the Structs for the Server Data.
cout << "Setting server data into the addrinfo struct.\n\n";
host_info.ai_family = AF_INET; //Set IP to handle TCP Connections
host_info.ai_socktype = SOCK_STREAM; //Sets the socket type to acccept TCP transmission
connStatus = getaddrinfo("google.com", "80", &host_info, &host_info_list); //Populates the structs with addrinfo of google on port 80
//Check if we were able to get data from the server
if(connStatus == ) cout << "Connection information populated successfuly\n\n";
else if(connStatus != ) cout << "Connection error: " << gai_strerror(connStatus) << endl;
cout << "Creating the socket now...";
int sock; //Descriptor for our socket
sock = socket(host_info_list->ai_family, host_info_list->ai_socktype, host_info_list->ai_protocol); //Opens internet socket with host, type, and protocol. This was all populated by getaddrinfo().
//Make sure the sock was created
if(sock == -1) cout << "Socket Error: " << endl; //Need to put error reporting in still
else cout << "Socket Created\n\n";
cout << "Connecting to the server...";
//Pass the connection code the Socket, the Address, and the Address length. return connection status
connStatus = connect(sock, host_info_list->ai_addr, host_info_list->ai_addrlen);
if(connStatus == -1) cout << "Connection Error: " << endl;
else cout << "You are now connected.\n\n";
cout << "Sending Data... \n\n";
//Msg to be sent
char *msg = "GET / HTTP/1.1\nhost: www.google.com\n\n";
int length; //Initialize msg lenghth
ssize_t bytesSent; //initialize bytesSent as a ssize_t
length = strlen(msg); //get length of msg for the buffer
//Tie to socket, send msg, give it the msg length for the buffer and set flags to 0. these are the same as write() function.
bytesSent = send(sock, msg, length, );
//Then we need to receive the data back from server
//The recv func will wait for a response to system.
cout << "Waiting to recieve data... \n";
ssize_t bytesReceived;
char buffer[5000]; //Set up a buffer to recveive data
bytesReceived = recv(sock, buffer, 5000, ); //Recv data
if(bytesReceived == ) cout << "Host disconnected.\n";
if(bytesReceived == -1) cout << "Connection error\n";
cout << bytesReceived << " bytes received :" << endl ;
cout << buffer << endl;
//If you open a door close it
cout << "Transaction success. Closing socket...\n";
freeaddrinfo(host_info_list); //Releases host information from memory
close(sock); //Closes the open socket on port 80
//That does it for this round. Not to bad to understand once you break it down.
}
Welcome, neophyte, to the real world.
Stay tuned for a python equivalent, and more tuts like this one with more advanced topics.
Plus if you have any request for tuts in this feild comment bellow to request it.
-revall