NetPad

The purpose of the app is to control remote hardware like Arduino, Netduino, Raspberry Pi ...

The protocol is TCP/IP (Client).

3 positions are handled either as text or bytes.

The range of the values x,y (1. control) and z (2. control) are between -100 and 100.

Byte Mode: 3 positions are transfered as 3 bytes (default)

ASCII Mode: 3 positions are transfered as text seperated by comma (ended by \n)

Session inactive: Each transmission in a serated connection

Session active: Connection never closed, but if necessary automatic reconnect (default)

Zero inactive: No return to zero values after release

Zero active: Auto return to zero values after release

The purpose of the app is to control remote hardware like Arduino, Netduino, Raspberry Pi ...

V1.1:

- Changed default mode

- Session to hold connection

V1.2:

- Tablet modifications

V1.3:

- Zero: Auto return to zero values on/off

- Remember last settings

V1.4

- Improved TCP/IP connection

Sample code for a server on Raspberry Pi:

#include "stdio.h"

#include "stdlib.h"

#include "string.h"

#include "unistd.h"

#include "sys/types.h"

#include "sys/socket.h"

#include "netinet/in.h"

void error(const char *msg)

{

perror(msg);

exit(1);

}

int main(int argc, char *argv[])

{

int sockfd, newsockfd, portno,n;

socklen_t clilen;

char buffer[256];

struct sockaddr_in serv_addr, cli_addr;

sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (sockfd < 0)

error("ERROR opening socket");

bzero((char *) &serv_addr, sizeof(serv_addr));

portno = 12345;

serv_addr.sin_family = AF_INET;

serv_addr.sin_addr.s_addr = INADDR_ANY;

serv_addr.sin_port = htons(portno);

if (bind(sockfd, (struct sockaddr *)

&serv_addr, sizeof(serv_addr)) < 0)

error("ERROR on binding");

while(1)

{

listen(sockfd,5);

clilen = sizeof(cli_addr);

newsockfd = accept(sockfd, (struct sockaddr *)

&cli_addr, &clilen);

if (newsockfd < 0)

error("ERROR on accept");

while(1)

{

bzero(buffer,256);

n = read(newsockfd,buffer,3);

if (n < 3)

{

error("ERROR reading from socket");

break;

}

float tmp1 = (float)buffer[0];

if (tmp1 > 127)

tmp1 -= 256;

float tmp2 = (float)buffer[1];

if (tmp2 > 127)

tmp2 -= 256;

float tmp3 = (float)buffer[2];

if (tmp3 > 127)

tmp3 -=256;

printf("%d %d %d\n",(int)tmp1,(int)tmp2,(int)tmp3);

}

close(newsockfd);

}

close(sockfd);

return 0;

}