ADIS_Projects/ADIS_Raspi_UDP/src/udp.c

/*
 * udp.c
 *
 * Author: Erich Styger
 * License: PDX-License-Identifier: BSD-3-Clause
 *
 * UDP example code by Paul Krzyzanowski, see
 * https://www.cs.rutgers.edu/~pxk/417/notes/sockets/udp.html
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include "hostname.h"
#include "platform.h"

#define BUFSIZE (64)

int udp_receive(int port) {
  struct sockaddr_in myaddr;  /* our address */
  struct sockaddr_in remaddr; /* remote address */
  socklen_t addrlen = sizeof(remaddr);    /* length of addresses */
  int recvlen;      /* # bytes received */
  int fd;       /* our socket */
  int msgcnt = 0;     /* count # of messages we received */
  static unsigned char buf[BUFSIZE]; /* receive buffer */

  /* create a UDP socket */
  if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("cannot create socket\n");
    return 0;
  }

  /* bind the socket to any valid IP address and a specific port */
  memset((char *)&myaddr, 0, sizeof(myaddr));
  myaddr.sin_family = AF_INET;
  myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  myaddr.sin_port = htons(port);

  if (bind(fd, (struct sockaddr *)&myaddr, sizeof(myaddr)) < 0) {
    perror("bind failed");
    return 0;
  }

  /* now loop, receiving data and printing what we received */
  for (;;) {
    printf("waiting on port %d\n", port);
    recvlen = recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *)&remaddr, &addrlen);
    if (recvlen > 0) {
      buf[recvlen] = 0;
      printf("received message: \"%s\" (%d bytes)\n", buf, recvlen);
    } else {
      printf("uh oh - something went wrong!\n");
    }
    sprintf((char*)buf, "ack %d", msgcnt++);
    printf("sending response \"%s\"\n", buf);
    if (sendto(fd, buf, strlen((char*)buf), 0, (struct sockaddr *)&remaddr, addrlen) < 0) {
      perror("sendto");
    }
  }
  /* never exits */
}


/* send a UDP datagram. Parameters are strings, e.g.
 * host IP, e.g. "10.180.254.51"
 * port number, e.g. "1234"
 * msg message string to send, e.g. "hello"
 * \return negative value in case of failure
 */
int udp_send(const char *host, int port, const char *msg) {
  struct sockaddr_in myaddr, remaddr;
  int fd, i;
  socklen_t slen=sizeof(remaddr);
  static char buf[BUFSIZE]; /* message buffer */
  int recvlen;    /* # bytes in acknowledgement message */
  int portNumber;
  char ipBuf[64]; /* in case 'host' is a hostname and not an IP address, this will hold the IP address */

  /* hostname to IP transformation */
  if (*host >='0' && *host<='9') { /* IP address */
    printf("IP: %s\n", host);
  } else {
    if (hostname_to_ip(host, ipBuf, sizeof(ipBuf))==0) {
      printf("hostname '%s' -> IP: '%s'\n", host, ipBuf);
      host = ipBuf; /* point to transformed IP address */
    } else {
      perror("hostname_to_ip() failed");
      return -1;
    }
  }

  /* create a socket */
  if ((fd=socket(AF_INET, SOCK_DGRAM, 0))==-1) {
    printf("socket created\n");
  }

  /* bind it to all local addresses and pick any port number */
  memset((char *)&myaddr, 0, sizeof(myaddr));
  myaddr.sin_family = AF_INET;
  myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  myaddr.sin_port = htons(0);

  if (bind(fd, (struct sockaddr *)&myaddr, sizeof(myaddr)) < 0) {
    perror("bind failed");
    return -1;
  }

  /* now define remaddr, the address to whom we want to send messages */
  /* For convenience, the host address is expressed as a numeric IP address */
  /* that we will convert to a binary format via inet_aton */
  memset((char *) &remaddr, 0, sizeof(remaddr));
  remaddr.sin_family = AF_INET;
  remaddr.sin_port = htons(port);
  if (inet_aton(host, &remaddr.sin_addr)==0) {
    fprintf(stderr, "inet_aton() failed\n");
    exit(1);
  }

  /* set socket timeout */
  struct timeval tv;
  tv.tv_sec = 5;
  tv.tv_usec = 0;
  if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO,&tv,sizeof(tv)) < 0) {
    perror("Error");
  }
  /* now let's send the messages */
  printf("Sending datagram '%s' to '%s' on port %d\n", msg, host, port);
  if (sendto(fd, msg, strlen(msg), 0, (struct sockaddr *)&remaddr, slen)==-1) {
    perror("sendto");
    exit(1);
  }

  /* now receive an acknowledgment from the server */
  recvlen = recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *)&remaddr, &slen);
  if (recvlen >= 0) {
    buf[recvlen] = '\0'; /* expect a printable string - terminate it */
    printf("response: \n%s\n", buf);
  } else { /* timeout */
    printf("socket receive timeout\n");
  }
  close(fd);
  return 0; /* ok */
}