How to send data using internet on C language windows - c

Question

I am pretty new to socket programming and the C language. I want to teleoperate a robot over the internet for that I have to send some values to a robot computer. Here is my code...
x = state.position_val[0];
y = state.position_val[1];
z = state.position_val[2];
Rx = state.gimbal_joints[0]*1000;
Ry= state.gimbal_joints[1]*1000;
Rz = state.gimbal_joints[2]*1000;
double arr[7] = { x, y, z, Rx, Ry, Rz, btonn };
SAFEARRAY* psa = SafeArrayCreateVector(VT_R8, 0, 7);
void* data;
SafeArrayAccessData(psa, &data);
CopyMemory(data, arr, sizeof(arr));
SafeArrayUnaccessData(psa);
return psa;
These are the code snippets under the while loop at each loop this code gets the state value of the robot and creates an array that is further used for teleoperation. I need to send this array over the internet to another computer.
Please help me how to do this?

Answer 1

I have tested this on Windows machine
Go to https://ngrok.com create an account
your robot should run ngrok client use following commands
ngrok authtoken xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
ngrok tcp 80
Forwarding tcp://3.tcp.ngrok.io:15842 -> localhost:80
Here ngrok will assign a local PORT to 80 and random port to outside network ie Interner exposed port. You have to add 80 and that port to your firewall rules of robot network device).
Goto https://whatismyipaddress.com/hostname-ip here put 3.tcp.ngrok.io Look IP address box from ngrok console out. You will get your robot's global IP. that you can connect to your robot from anywhere in the world.
Following are the Client and Server examples that you can compile and run.
gcc .\Client.c -o Client
gcc .\Server.c -o Server
Client.c
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
//Create a Socket for server communication
short SocketCreate(void)
{
short hSocket;
printf("Create the socket\n");
hSocket = socket(AF_INET, SOCK_STREAM, 0);
return hSocket;
}
//try to connect with server
int SocketConnect(int hSocket)
{
int iRetval=-1;
int ServerPort = 15842; // ngroks external tcp port
struct sockaddr_in remote= {0};
remote.sin_addr.s_addr = inet_addr("3.134.xxx.xxx"); //Robot IP
remote.sin_family = AF_INET;
remote.sin_port = htons(ServerPort);
iRetval = connect(hSocket,(struct sockaddr *)&remote,sizeof(struct sockaddr_in));
return iRetval;
}
// Send the data to the server and set the timeout of 20 seconds
int SocketSend(int hSocket,char* Rqst,short lenRqst)
{
int shortRetval = -1;
struct timeval tv;
tv.tv_sec = 20; /* 20 Secs Timeout */
tv.tv_usec = 0;
if(setsockopt(hSocket,SOL_SOCKET,SO_SNDTIMEO,(char *)&tv,sizeof(tv)) < 0)
{
printf("Time Out\n");
return -1;
}
shortRetval = send(hSocket, Rqst, lenRqst, 0);
return shortRetval;
}
//receive the data from the server
int SocketReceive(int hSocket,char* Rsp,short RvcSize)
{
int shortRetval = -1;
struct timeval tv;
tv.tv_sec = 20; /* 20 Secs Timeout */
tv.tv_usec = 0;
if(setsockopt(hSocket, SOL_SOCKET, SO_RCVTIMEO,(char *)&tv,sizeof(tv)) < 0)
{
printf("Time Out\n");
return -1;
}
shortRetval = recv(hSocket, Rsp, RvcSize, 0);
printf("Response %s\n",Rsp);
return shortRetval;
}
//main driver program
int main(int argc, char *argv[])
{
int hSocket, read_size;
struct sockaddr_in server;
char SendToServer[100] = {0};
char server_reply[200] = {0};
//Create socket
hSocket = SocketCreate();
if(hSocket == -1)
{
printf("Could not create socket\n");
return 1;
}
printf("Socket is created\n");
//Connect to remote server
if (SocketConnect(hSocket) < 0)
{
perror("connect failed.\n");
return 1;
}
printf("Sucessfully conected with server\n");
printf("Enter the Message: ");
gets(SendToServer);
//Send data to the server
SocketSend(hSocket, SendToServer, strlen(SendToServer));
//Received the data from the server
read_size = SocketReceive(hSocket, server_reply, 200);
printf("Server Response : %s\n\n",server_reply);
close(hSocket);
shutdown(hSocket,0);
shutdown(hSocket,1);
shutdown(hSocket,2);
return 0;
}
Server.c
#include<stdio.h>
#include<string.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
short SocketCreate(void)
{
short hSocket;
printf("Create the socket\n");
hSocket = socket(AF_INET, SOCK_STREAM, 0);
return hSocket;
}
int BindCreatedSocket(int hSocket)
{
int iRetval=-1;
int ClientPort = 80; //Robot local port
struct sockaddr_in remote= {0};
/* Internet address family */
remote.sin_family = AF_INET;
/* Any incoming interface */
remote.sin_addr.s_addr = htonl(INADDR_ANY);
remote.sin_port = htons(ClientPort); /* Local port */
iRetval = bind(hSocket,(struct sockaddr *)&remote,sizeof(remote));
return iRetval;
}
int main(int argc, char *argv[])
{
int socket_desc, sock, clientLen, read_size;
struct sockaddr_in server, client;
char client_message[200]= {0};
char message[100] = {0};
const char *pMessage = "hello aticleworld.com";
//Create socket
socket_desc = SocketCreate();
if (socket_desc == -1)
{
printf("Could not create socket");
return 1;
}
printf("Socket created\n");
//Bind
if( BindCreatedSocket(socket_desc) < 0)
{
//print the error message
perror("bind failed.");
return 1;
}
printf("bind done\n");
//Listen
listen(socket_desc, 3);
//Accept and incoming connection
while(1)
{
printf("Waiting for incoming connections...\n");
clientLen = sizeof(struct sockaddr_in);
//accept connection from an incoming client
sock = accept(socket_desc,(struct sockaddr *)&client,(socklen_t*)&clientLen);
if (sock < 0)
{
perror("accept failed");
return 1;
}
printf("Connection accepted\n");
memset(client_message, '\0', sizeof client_message);
memset(message, '\0', sizeof message);
//Receive a reply from the client
if( recv(sock, client_message, 200, 0) < 0)
{
printf("recv failed");
break;
}
printf("Client reply : %s\n",client_message);
if(strcmp(pMessage,client_message)==0)
{
strcpy(message,"Hi there !");
}
else
{
strcpy(message,"Invalid Message !");
}
// Send some data
if( send(sock, message, strlen(message), 0) < 0)
{
printf("Send failed");
return 1;
}
close(sock);
sleep(1);
}
return 0;
}
You can now send receive data between robot and your computer