First commit

main.c

@@ -0,0 +1,155 @@
+#include <sys/socket.h>
+#include <stdlib.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+int create_socket(int network, char transport) {  
+
+/* 'network' contains 4 for ipv4 or 6 for ipv6. 
+   'transport' contains 'T' for TCP or 'U' for UDP. 
+   The function returns -1 if the paramters do not match the above statement. */
+
+	int domain;
+	int type;
+
+	if (network == 4) {
+		domain = AF_INET;
+	} else if (network == 6) {
+		domain = AF_INET6;
+	} else {
+		return -1;
+	}
+
+	if (transport == 'T') {
+		type = SOCK_STREAM;
+	} else if (transport == 'U') {
+		type = SOCK_DGRAM;
+	} else {
+		return -1;
+	}
+
+	int newSock = socket(domain,type,0);
+	return newSock;
+}
+
+
+void create_addr(int network, char* address, int port,struct sockaddr* dest) {
+/* Takes the relevant values - network (4 or 6), address, port - and fills them
+   into dest */
+
+	if (network == 4) {
+		struct sockaddr_in listen_address;
+		
+		listen_address.sin_family = AF_INET;
+		listen_address.sin_port = htons(port);
+		inet_pton(AF_INET,address,&listen_address.sin_addr);
+		memcpy(dest,&listen_address,sizeof(listen_address));
+		return;	
+
+	} else if (network == 6) {
+		struct sockaddr_in6 listen_ipv6;
+		listen_ipv6.sin6_family = AF_INET6;
+		listen_ipv6.sin6_port = htons(port);
+		inet_pton(AF_INET6,address,&listen_ipv6.sin6_addr);
+		memcpy(dest,&listen_ipv6,sizeof(listen_ipv6));
+		return;
+
+	} else {
+		exit(-2);
+	}
+		
+}
+
+
+
+
+
+int create_and_bind (int network, char transport, char* address, int port,struct sockaddr* addr_struct) {
+/* combines the socket creation and address creation into one
+   function - simply pass the required values, and a structure,
+   and this function does the legwork for you */
+
+	int socket = create_socket(network,transport);
+	if (socket == -1) {
+		exit(-1);
+	}
+	create_addr(network,address,port,addr_struct);
+	int addrlen = sizeof(*addr_struct);
+	int i = bind (socket,addr_struct,(socklen_t)addrlen);
+	if (i < 0) {
+		exit(-3);
+	}
+	return socket;
+}
+
+int create_remote (int network,char transport,char* address,int port) {
+/* same as 'create_and_bind', but for remote sockets - client rather
+   than server sockets */
+
+	int socket = create_socket(network,transport);
+	if (socket == -1) {
+                exit(-1);
+        }
+	struct sockaddr remote_addr_struct;
+        create_addr(network,address,port,&remote_addr_struct);
+        int addrlen = sizeof(remote_addr_struct);
+        int i = connect(socket,&remote_addr_struct,(socklen_t)addrlen);
+	if (i < 0) {
+		printf("Something went wrong: %s\n",strerror(errno));
+		exit(-3);
+	}
+        return socket;
+}
+
+void forward_data(int from_fd, int to_fd) {
+	int n = 0;
+        char* buffer = malloc(3000*sizeof(char));
+	while ((n = recv(to_fd, buffer, 3000, 0)) > 0) { // read data from input socket
+        	send(to_fd, buffer, n, 0); // send data to output socket
+	}
+}
+
+int main() {
+
+	int preferred_network = 4;
+	char preferred_transport = 'T';
+	struct sockaddr addr_struct;
+	int server_sock = create_and_bind(preferred_network,preferred_transport,"127.0.0.1",3000,&addr_struct);
+	int addrlen = sizeof(addr_struct);
+
+	listen(server_sock,50);  /* Arbitrary number, change later */
+
+	while (1) {
+	int from_client = accept(server_sock,&addr_struct,(socklen_t *)&addrlen);	
+	int to_server = create_remote(preferred_network,preferred_transport,"127.0.0.1",5000);
+	
+	if (fork() == 0) {
+
+	/* fork returns 0 for a child, so we're in the child's execution
+	   right now */
+		close(server_sock);
+		if (fork() == 0) {
+			forward_data(from_client,to_server);
+			exit(0);
+		}
+		if (fork() == 0) {
+			forward_data(to_server,from_client);
+			exit(0);
+		}
+		exit(0);
+
+
+	}
+//	recv(from_client,buffer,3000,0);
+			
+
+//	printf("%s",buffer);
+	
+
+	}
+
+}
+