Linux

 

   #define MAX_MSG_LEN 1200 /* max size of any msg */

   struct UDP{ /*to perform chat*/
       char username[16];
       char msg[100];
       unsigned long userIP;
       unsigned short portnumber;
  } UDPchatee;    


  /************** UDP variables *************/
  int UDP_socketID;
  struct sockaddr_in serverAddr; //server details!
  struct RegMsg *RegMessage; //registration message sent to server
  int size = sizeof(serverAddr); //size of serverAddr
  RegRespMsg_t RespMessage; //this is the response message received from
  server after UDP connection
  struct in_addr userIP;
  /****************************************/

  /* variables used in both protocols */
  int i; //the for-loop counter
  int check; //this variable store the return values of sendto and receive
  functions to make sure transmission is correct

  /************ UDP variables for chat *****************/
  char username[14];
  int userfound; //flag that is set to 1 when user name type in exists
  char message_sent[MAX_MSG_LEN];
  int len; //message length
  int UDP_socket;
  struct sockaddr_in chateeAddr; //address of user you want to chat to
  struct UDP *UdpChat;
  int sizec = sizeof(chateeAddr);
  char prompt[10]; //user response when asked to continue chatting
  /*********************************************/

  /* UDP Chat */
    //get the user name and IP you want to talk to
    for (i=0; i < 16; i++)
      username[i]= '\0';
    printf("\nPlease type user name you want to talk to: ");
    fgets(username, MAX_MSG_LEN, stdin);
    strcpy(UDPchatee.username, username);
    UDPchatee.username[strlen(UDPchatee.username)-1] = '\0'; //remove the '\n' character
    userfound=-1;

    for(i = 0; i< ntohl(RespMessage.nusers); i++)
     {
        if(strcmp(UDPchatee.username, RespMessage.user[i].username) == 0)
        {
            UDPchatee.userIP = RespMessage.user[i].ipAddr;
            UDPchatee.portnumber = RespMessage.user[i].udpPort;
            userfound = i;
        }
    }
    if(userfound == -1){
        printf("The username does not exist! Try again.\n\n");
        continue;
    }

    //(1) Get a UDP socket //
    UDP_socket = socket(AF_INET, SOCK_DGRAM, 0);
    char msg[100], b1[100];

    //(2) Store the information of server inside the chateeAddr structure,
    bzero((char *)&chateeAddr,sizeof(chateeAddr));
    chateeAddr.sin_family = AF_INET;
    chateeAddr.sin_port = UDPchatee.portnumber; //get port number
    chateeAddr.sin_addr.s_addr = UDPchatee.userIP; //get ip address
    memset(chateeAddr.sin_zero, '\0', sizeof chateeAddr.sin_zero);
    
    while(1)
        {
                //get message you want to send
        printf("\nEnter a line of text as your message: ");
                fgets(msg,MAX_MSG_LEN,stdin);
        strcpy(UDPchatee.msg, msg);
                check = sendto(UDP_socket,UdpChat,sizeof(UDPchatee),0,(struct sockaddr *)&chateeAddr,sizec);
        if (check == -1)
          printf("Sending is in error!\n\n");
                check = recvfrom(UDP_socket,b1,sizeof(b1),0,(struct sockaddr *)&chateeAddr,&sizec);
        if (check == -1)
          printf("Receiving is in error\n");
                printf("\nReply: %s",b1);
        }