My prototype webserver-thing

server.c

#include "xeric-utils.h"

/* The main method. */
int main(int argc, char * argv[]) {
	int i;
	int port = 80;
	struct in_addr address = {0};

	/* Parse the arguments: */
	for(i = 1; i < argc; i++) {
		if(strcmp(argv[i], "--port") == 0) {
			i++;

			if(i == argc) {
				warn("Expected port number after --port option. Continuing with port 80.");
				break;
			}

			port = strtoport(argv[i]);

			if(!port) {
				warn("Invalid port number specified. Continuing with port 80.");
				port = 80;
			}
		} else if(strcmp(argv[i], "--address") == 0) {
			i++;

			if(i == argc) {
				warn("Expected address after --address option. Continuing with address 0.0.0.0.");
				break;
			}

			if(inet_pton(AF_INET, argv[i], &address) != 1) {
				warn("Invalid address specified. Continuing with address 0.0.0.0.");
			}
		} else {
			printf("Unrecognized option %s.\n", argv[i]);
		}
	}

	int client;
	socklen_t clilen = sizeof(struct sockaddr_in);
	char buffer[1024];
	char str_address[16];
	struct sockaddr_in serv_addr, cli_addr;
	int n;

	/* Create the socket: */
	s = socket(AF_INET, SOCK_STREAM, 0);

	if(s < 0) {
		warn("Error opening socket.");
		return 1;
	}

	/* Listen on the socket: */
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(port);
	serv_addr.sin_addr = address;

	errno = 0;

	if(bind(s, (struct sockaddr *) &serv_addr, sizeof serv_addr) < 0) {
		if(errno == EADDRINUSE)
			warn("Could not bind to port; already in use.");
		else
			warn("Could not bind to port due to an unknown error.");

		return 1;
	}

	listen(s, 5);

	success("Xeric 0.1.0 has started!");

	inet_ntop(AF_INET, &serv_addr.sin_addr, str_address, 15);
	printf("Listening at %s:%d.\n", str_address, port);

	/* Enable the Ctrl+C SIGINT handler so that the socket can be closed */
	signal(SIGINT, interrupted);

	while(keepRunning) {
		/* Accept a client: */
		client = accept(s, (struct sockaddr *)&cli_addr, &clilen);

		if(client < 0) {
			warn("Error on accept.");
			return 1;
		}

		ip4_t r_addr = {cli_addr.sin_addr.s_addr};
		printf("Got client from %d.%d.%d.%d.\n", r_addr.components.p1, r_addr.components.p2, r_addr.components.p3, r_addr.components.p4);

		/* Read data from the client: */
		bzero(buffer, 1024);
		n = read(client, buffer, 1023);

		if(n < 0) {
			warn("Error reading from socket; breaking connection.");
			goto close;
		}

		puts(buffer);

		/* Write data to the client: */
		const char * output = "HTTP/1.1 200 OK\nContent-Type: text/html\n\n<h1>It works!</h1> <p>Welcome to Xeric, the tiny server.</p>";
		n = write(client, output, strlen(output));

		if(n < 0) {
			warn("Error writing to socket; breaking connection.");
			goto close;
		}

	close:
		/* Close the connection: */
		close(client);
	}

	if(s >= 0) {
		close(s);
	}

	return 0;
}

xeric-utils.h

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/* Some message output methods. */
#ifdef _WIN32
	#define warn puts
	#define success puts
#else
	void warn(const char * message) {
		printf("\033[22;33m%s\n\033[22;0m", message);
	}

	void success(const char * message) {
		printf("\033[22;32m%s\n\033[22;0m", message);
	}
#endif

/* Represents an IPv4 address.                                  *
 * We use this to convert the `unsigned long` from sockaddr_in. */
typedef union {
	unsigned long address;

	struct {
		unsigned char p1;
		unsigned char p2;
		unsigned char p3;
		unsigned char p4;
	} components;
} ip4_t;

/* Handles interrupts gracefully.                            *
 * Oddly, however, interrupting currently causes a segfault. * <-- Actually, it doesn't anymore... uh-oh.
 * I have no idea where that comes from.                     */
int keepRunning = 1;
int s;

void interrupted(int sig) {
	/* Tell it to stop running: */
	keepRunning = 0;

	/* Close the socket: */
	close(s);
	s = -1;

	/* Make it possible to "really kill": */
	signal(SIGINT, SIG_DFL);
}

/* Parses a port number, since strtoll isn't available in C89. */
int strtoport(const char * str) {
	int p = 0;
	int v;

	while(*str) {
		v = *str++ - '0';

		if(v < 0 || v > 9)
			return 0;

		p = p * 10 + v;

		if(p > 65535)
			return 0;
	}

	return p;
}