Telematik

• tcp- client realisieren
• tcp- forwarder realisieren

//simple tcp-client like nc
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
 
#include <stdio.h>
 
int main () {
	unsigned int tcp_remoteport = 7770;
 
	char tcp_remotehost[16] = "127.000.000.001";
 
	char buffer[256] = "";
 
	int client_socket_fd;
 
	struct sockaddr_in client_socket = { 0 };
 
 
	//-----------------Client Part----------------------------------------------
	//create a new socket
	if ( (client_socket_fd=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) == -1) {
		printf("Client-error: can't create socket\n");
		exit(0);
	}
 
	//socket setup
	client_socket.sin_family=AF_INET;
	client_socket.sin_port = htons(tcp_remoteport);
	client_socket.sin_addr.s_addr = inet_addr(tcp_remotehost);
	//--------------------------------------------------------------------------
 
	if (connect(client_socket_fd,(struct sockaddr*) &client_socket, 
				sizeof(client_socket)) != -1) {
		while (1) {
			printf(">>");
			scanf("%s", buffer);
			sprintf(buffer,"%s\n",buffer);
			write(client_socket_fd,buffer,sizeof(buffer)-1);
 
			if (read(client_socket_fd,buffer,sizeof(buffer)-1) != -1) {
				printf("<<%s",buffer);
			}
		}
	} else {
		printf("Client-error: can't connect to %s:%d\n",tcp_remotehost,
				tcp_remoteport);
	}
}

//simple tcp-forwarder
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
 
int main () {
	unsigned int tcp_listenport = 7777;
	unsigned int tcp_remoteport = 7770;
 
	char tcp_remotehost[16] = "127.000.000.001";
	char tcp_serverinterface[16] = "000.000.000.000";
 
	char buffer[256] = "";
 
	int accepted_server_socket_len;
	int server_socket_fd,accepted_server_socket_fd;
 
 
	int client_socket_fd;
 
	int server_socket_size,client_socket_size;
 
	int on;
 
	struct sockaddr_in server_socket = { 0 };
	struct sockaddr_in accepted_server_socket = { 0 };
 
	struct sockaddr_in client_socket = { 0 };
 
	//-----------------Server Part---------------------------------------------
	//create a new socket
	if ( (server_socket_fd=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) == -1) {
		printf("Server-error: can't create socket\n");
		exit(0);
	}
 
	//turn off bind adress
	on=1;
	if ( setsockopt(server_socket_fd,SOL_SOCKET,SO_REUSEADDR,(const char *) &on,
					sizeof(on)) == -1)
		printf("Server-warning: unable release binding\n",tcp_listenport);
 
 
	//allow access from 0.0.0.0
	server_socket.sin_addr.s_addr=inet_addr(tcp_serverinterface);
	server_socket.sin_family=AF_INET;
	server_socket.sin_port = htons(tcp_listenport);
 
	//bind to interface/ip
	if ( bind(server_socket_fd,(struct sockaddr *) &server_socket,
				sizeof(server_socket)) == -1) {
		printf("Server-error: unable binding on port %d\n",tcp_listenport);
		close(server_socket_fd);
		exit(0);
	}
 
	//listen
	if ( listen(server_socket_fd,1) ) {
		printf("Server-error: unable binding on port %d\n",tcp_listenport);
		close(server_socket_fd);
		exit(0);
	}
	//--------------------------------------------------------------------------
 
	//-----------------Client Part----------------------------------------------
	//create a new socket
	if ( (client_socket_fd=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) == -1) {
		printf("Client-error: can't create socket\n");
		exit(0);
	}
 
	//socket setup
	client_socket.sin_family=AF_INET;
	client_socket.sin_port = htons(tcp_remoteport);
	client_socket.sin_addr.s_addr = inet_addr(tcp_remotehost);
	//--------------------------------------------------------------------------
 
	while (1) {
		accepted_server_socket_len=sizeof(accepted_server_socket_len);
		if ( (accepted_server_socket_fd=accept(server_socket_fd,
				(struct sockaddr *) &accepted_server_socket,
				&accepted_server_socket_len)) != -1) {
			if (connect(client_socket_fd,(struct sockaddr*) &client_socket,
						sizeof(client_socket)) != -1) {
				while (1) {
					//transmit data from server part to client part
					if (read(accepted_server_socket_fd,buffer,
							sizeof(buffer)-1) != -1) {
						printf(">>%s",buffer); 
						write(client_socket_fd,buffer,sizeof(buffer));
					}
					printf("data\n");
					//transmit data from client part to server part
					if (read(client_socket_fd,buffer,
							sizeof(buffer)-1) != -1) {
						printf("<<%s",buffer); 
						write(accepted_server_socket_fd,buffer,sizeof(buffer));
					}
				}
			} else {
				printf("Client-error: can't connect to %s:%d\n",tcp_remotehost,
						tcp_remoteport);
			}
		}
		close(accepted_server_socket_fd);
	}
}