#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MAXPENDING 5    /* Maximum outstanding connection requests */

int main(int argc, char *argv[]) {
  int servSock;                    /* Socket descriptor for server */
  int clntSock;                    /* Socket descriptor for client */
  struct sockaddr_in echoServAddr; /* Local address */
  struct sockaddr_in echoClntAddr; /* Client address */
  unsigned short echoServPort;     /* Server port */
  unsigned int clntLen;            /* Length of client address data structure */

  if (argc != 2) {
    fprintf(stderr, "Usage:  %s <Server Port>\n", argv[0]);
    exit(1);
  }

  echoServPort = atoi(argv[1]);  /* First arg:  local port */

  /* Create socket for incoming connections */
  if ((servSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
    printf("socket() failed\n");
    exit(1);
  }
      
  /* Construct local address structure */
  memset(&echoServAddr, 0, sizeof(echoServAddr));   /* Zero out structure */
  echoServAddr.sin_family = AF_INET;                /* Internet address family */
  echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
  echoServAddr.sin_port = htons(echoServPort);      /* Local port */

  /* Bind to the local address */
  if (bind(servSock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0) {
    printf("bind() failed\n");
    exit(1);
  }

  /* Mark the socket so it will listen for incoming connections */
  if (listen(servSock, MAXPENDING) < 0) {
    printf("listen() failed\n");
    exit(1);
  }

  for (;;) {
    /* Set the size of the in-out parameter */
    clntLen = sizeof(echoClntAddr);

    /* Wait for a client to connect */
    if ((clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr, &clntLen)) < 0) {
      printf("accept() failed\n");
      exit(1);
    }

    printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));

    char echoBuffer[80];
    int bytes_recv = recv(clntSock, echoBuffer, 80, 0);

    printf("%d bytes received\n", bytes_recv);

    send(clntSock, echoBuffer, bytes_recv, 0);

    close(clntSock);
  }
}