C linux proxy server - c++

Question

I'm trying to build a client -> proxy server -> server application.
I need help with the proxy server, how do i make it send data to the server right now it can only communicate with the client.
Here is my codef or the proxy server, I modified it from an example. I'm new at this.
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno, pid;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
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)
error("ERROR on binding");
listen(sockfd,5);
clilen = sizeof(cli_addr);
while (1) {
newsockfd = accept(sockfd,
(struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");
pid = fork();
if (pid < 0)
error("ERROR on fork");
if (pid == 0) {
close(sockfd);
dostuff(newsockfd);
exit(0);
}
else close(newsockfd);
} /* end of while */
close(sockfd);
return 0; /* we never get here */
}
/******** DOSTUFF() *********************
There is a separate instance of this function
for each connection. It handles all communication
once a connnection has been established.
*****************************************/
void dostuff (int sock)
{
int n, p;
char buffer[256];
char request;
FILE *file;
file = fopen("process.log","a+");
do
{
//here the proxy server receives data from the client
bzero(buffer,256);
p = read(sock,buffer,255);
if (n < 0) error("ERROR reading from socket");
printf("num: %s\n",buffer);
//here the proxy servers replies to the client.
n = write(sock,buffer,sizeof(buffer));
//here the process should send data to the server
//...codes i need help with...
if (n < 0) error("ERROR writing to socket");
fprintf(file,"%s\n",buffer); /*writes*/
}while(p != 0); //this runs the process +1 more than it should. wonder why?
fclose(file);
}
DoStuff() .... you can also check the comments I added.
Also how do I send a message to the client as soon as the client is connected to the server, something like a welcome client message? :)
note: the proxy server sends a GET request to a HTTP 1.1 server.
I would really appreciate it. Thanks :)

Answer 1

To connect to the server, you're going to have to call socket and then connect to get that socket connected to your real server from the proxy. See section 5 here:
http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html
Additionally, check p instead of n 4 lines into your do-while loop in DoStuff().