Networking, Part 6: Building a web server - angrave/SystemProgramming GitHub Wiki
A web server needs to implement HTTP (Hypertext transfer protocol), which is a specification of how client machine can request resources from a server and how a server can respond to a client message.
We're not going to build a fully compliant web server. Instead we will build the simplest possible web server, using the parts of TCP server that have already been introduced.
First, we'll set up a passive server socket
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
getaddrinfo(NULL, "0", &hints, &result); // "0" = use any port that is freeWe don't need the timeout after we've finished using the port - it can be reused immediately,
int optval = 1;
setsockopt(sock_fd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));Bind the socket to a port on the local machine and start listening for connections
bind(sock_fd, result->ai_addr, result->ai_addrlen)
listen(sock_fd, 10)Now that we've bound to a port, we can find out the actual port number used. Notice we need convert it from network to host byte ordering, (ntohs)
struct sockaddr_in sin;
socklen_t socklen = sizeof(sin);
getsockname(sock_fd, (struct sockaddr *)&sin, &socklen)
printf("Listening on port %d\n", ntohs(sin.sin_port)) Now call accept block until we have a client request to service. For each client, wait for the web browser's request then always send a friendly message back. This starts with the response header that includes the MIMETYPE - the type of data that is represented by the bytes that follow. The response header, like the request header is terminated by two blank lines together \r\n\r\n/ Note this code also demonstrates use of Linux's dprintf which allows printf-like formatting directly to a file descriptor.
while(1) {
int client_fd = accept(sock_fd, (struct sockaddr*) &client_info, &size);
char *connected_ip= inet_ntoa(client_info.sin_addr);
// ^^^^ Does this look thread-safe to you?
int port = ntohs(client_info.sin_port);
char buffer[1000];
read(client_fd, buffer, sizeof(buffer)-1);
dprintf(client_fd, "HTTP/1.0 200 OK\r\n");
dprintf(client_fd, "Content-Type: text/html\r\n\r\n");
dprintf(client_fd, "<html><body><h1>Hello</h1></body></html>");
shutdown(client_fd , SHUT_RDWR);
close(client_fd);
} FILE*file = fopen("apicture.jpg","r");
if(file) {
fseek(file,0, SEEK_END);
long size = ftell(file);
fseek(file,0,SEEK_SET);
printf("Sending %ld bytes\n", size);
char*buf = malloc(size);
fread(buf,1,size,file);
char response[2048];
sprintf( response, "HTTP/1.0 200 OK\r\n"
"Content-Type: image/jpeg\r\n"
"Content-Length: %ld\r\n\r\n" , size);
write(client_fd, response, strlen(response));
write(client_fd, buf, size);
fclose(file);
free(buf);
}
shutdown(client_fd , SHUT_RDWR);
close(client_fd);