Transmitting audio through socket (UDP) but not playing back properly - c

Question

I'm trying to transmit from the client side a wav file through socket (UDP) and have the server playing the wav file by means of the ALSA library.
Since my coding level in C is very low I've first learnt how to set up a communication between client and server via sockets and interchange text messages.
Afterwards I've learnt how to play a wav file with ALSA by redirecting the stdin when running the playback app.
I've tried to joint both code (UDPServer.c + playback.c) files and when I pass the stdin to the UDPClient.c file it sends it to the UDPServer.c but it's just a pure tone instead of the actual music file that I'm trying to pass.
I don't know how exactly to pass the file into the UDPClient.c in order for it to send it to the socket to the server.
UDPServer.c
// Server side implementation of UDP client-server model
// Libraries
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <alsa/asoundlib.h>
// CONSTANTS
#define PORT 8080
#define MAXLINE 2048
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
// FUNCTION DECLARATION
int audio_play (char signal);
// Main code
int main() {
int sockfd;
char buffer[MAXLINE];
char *hello = "AUDIO PLAYBACK FINISH";
struct sockaddr_in servaddr, cliaddr;
// Creating socket file descriptor
if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
memset(&servaddr, 0, sizeof(servaddr));
memset(&cliaddr, 0, sizeof(cliaddr));
// Filling server information
servaddr.sin_family = AF_INET; // IPv4
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(PORT);
// Bind the socket with the server address
if ( bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0 ) {
perror("bind failed");
exit(EXIT_FAILURE);
}
int len, n;
len = sizeof(cliaddr); //len is value/result
// Receive a mesage from the socket
n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL, ( struct sockaddr *) &cliaddr, &len);
buffer[n] = '\0';
//printf("Client : %s\n", buffer);
audio_play(buffer);
// Send a message on the socket
sendto(sockfd, (const char *)hello, strlen(hello), MSG_CONFIRM, (const struct sockaddr *) &cliaddr, len);
printf("PLAYING AUDIO???.\n");
return 0;
}
// FUNCTIONS
int audio_play (char s)
{
long loops;
int rc;
int size;
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
unsigned int val;
int dir;
snd_pcm_uframes_t frames;
char *buffer;
/* Open PCM device for playback. */
rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
if (rc < 0) {
fprintf(stderr, "unable to open pcm device: %s\n", snd_strerror(rc));
exit(1);
}
/* Allocate a hardware parameters object. */
snd_pcm_hw_params_alloca(&params);
/* Fill it in with default values. */
snd_pcm_hw_params_any(handle, params);
/* Set the desired hardware parameters. */
/* Interleaved mode */
snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
/* Signed 16-bit little-endian format */
snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
/* Two channels (stereo) */
snd_pcm_hw_params_set_channels(handle, params, 2);
/* 48000 bits/second sampling rate */
val = 48000;
snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);
/* Set period size to 32 frames. */
frames = 32;
snd_ pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
/* Write the parameters to the driver */
rc = snd_pcm_hw_params(handle, params);
if (rc < 0) {
fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(rc));
exit(1);
}
/* Use a buffer large enough to hold one period */
snd_pcm_hw_params_get_period_size(params, &frames, &dir);
size = frames * 4; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params, &val, &dir);
/* 5 seconds in microseconds divided by
* period time */
loops = 5000000 / val;
while (loops > 0) {
loops--;
// rc = read(0, buffer, size);
rc = s;
if (rc == 0) {
fprintf(stderr, "end of file on input\n");
break;
} else if (rc != size) {
fprintf(stderr, "short read: read %d bytes\n", rc);
}
rc = snd_pcm_writei(handle, buffer, frames);
if (rc == -EPIPE) {
/* EPIPE means underrun */
fprintf(stderr, "underrun occurred\n");
snd_pcm_prepare(handle);
} else if (rc < 0) {
fprintf(stderr, "error from writei: %s\n", snd_strerror(rc));
} else if (rc != (int)frames) {
fprintf(stderr, "short write, write %d frames\n", rc);
}
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
}
UDPClient.c
// Client side implementation of UDP client-server model
// Libraries
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
// CONSTANTS
#define PORT 8080
#define MAXLINE 2048
// Main code
int main(int argc, char **argv) {
int sockfd;
char buffer[MAXLINE];
char *data = "Here is where the file of audio should be?";
struct sockaddr_in servaddr;
// Creating socket file descriptor
if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
memset(&servaddr, 0, sizeof(servaddr));
// Filling server information
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(PORT);
servaddr.sin_addr.s_addr = INADDR_ANY;
int n, len;
// Send a message on the socket
sendto(sockfd, (const char *)data, strlen(data), MSG_CONFIRM, (const struct sockaddr *) &servaddr, sizeof(servaddr));
printf("AUDIO SENT.\n");
// Receive a message from the socket
n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL, (struct sockaddr *) &servaddr, &len);
buffer[n] = '\0';
printf("Server : %s\n", buffer);
close(sockfd);
return 0;
}