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Author: greeshmap

EchoClient.c

@@ -0,0 +1,253 @@
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#define PORT 10609
+#define SIZE 1000
+
+typedef struct 
+{
+	unsigned int length;
+	unsigned char data[SIZE];
+} Message;
+
+typedef enum
+{ 	
+	Ok, 		// operation successful
+	Bad, 		// unrecoverable error
+	Wronglength // bad message length supplied
+}Status;
+
+typedef struct sockaddr_in SocketAddress;
+
+
+struct hostent *gethostbyname() ;
+void makeDestSA(SocketAddress * sa, char *hostname, int port) ;
+void printSA(SocketAddress sa);
+void makeLocalSA(SocketAddress *sa) ;
+void makeDestSA(SocketAddress * sa, char *hostname, int port);
+Status anyThingThere(int s);
+Status UDPsend(int s, Message *m, SocketAddress destination);
+Status UDPreceive(int s, Message *m, SocketAddress *origin);
+Status DoOperation (Message *message, Message *reply, int s, SocketAddress serverSA);
+
+
+void main(int argc, char **argv)
+{
+	//Server's host name must be entered as an argument else the program exits
+	if(argv[1] == NULL){
+		printf("Server host name not entered..exiting\n");
+		exit(1);
+	}
+	
+	int s, port=PORT, n=0;
+	Message message1, message2;
+	SocketAddress mySocketAddress, yourSocketAddress;
+	memset(&message1, 0, sizeof(message1));  
+
+	//Create a socket, if failed to, exit from the program
+	if(( s = socket(AF_INET, SOCK_DGRAM, 0))<0) {
+		perror("socket failed");
+		return;
+	}
+
+	//call makeLocalSA to make a socket address using any of the addressses of this computer for a local socket on any port 
+	makeLocalSA(&mySocketAddress);
+	
+	//Bind to the local port, if failes to, close the socket and then return
+	if( bind(s, (struct sockaddr *)&mySocketAddress, sizeof(struct sockaddr_in))!= 0){
+		perror("Bind failed\n");
+		close (s);
+		return;
+	}
+	
+	//prints socket address  
+	
+	printSA(mySocketAddress);
+	makeDestSA(&yourSocketAddress, argv[1], port);
+	
+	while(1)
+	{
+		printf("Enter the message to be sent to server\n");
+		
+	//Reads the message from user
+    	fgets(message1.data, SIZE, stdin); 
+    	char *pos;
+    	if((pos=strchr(message1.data, '\n')) != NULL)
+    	{
+    	//If the message does not have null in the end, adds null
+    		*pos = '\0';
+    	}
+    	else
+    	{
+    		printf("Input too long for buffer\n");
+    		exit(1);
+    	}
+		message1.length=strnlen(message1.data, SIZE);
+		
+		//call DoOperation function: sends message to the server and waits till a reply is received from the server
+		DoOperation(&message1, &message2, s, yourSocketAddress);
+		
+		//client waits for 2 seconds before sending next message: sends peridic requests
+		sleep(2);
+	}
+}
+
+
+/*sends a given request message to a given socket address and blocks until it returns with a reply message and returns status*/
+Status DoOperation (Message *message, Message *reply, int s, SocketAddress serverSA)
+{
+	Status status=Ok;
+	int n=0;
+	SocketAddress receiveSA;
+	memset(&receiveSA, 0, sizeof(receiveSA));
+    	socklen_t addrlen = sizeof(receiveSA);
+    
+   	//if status returned by UDPsend is Ok, continue to wait for receive else set the status to bad
+	if( (status=UDPsend(s, message, serverSA)) ==Ok)
+	{
+		printf("Message sent ..waiting for the server to reply\n");
+	}		
+	else
+	{
+		status=Bad;
+		printf("Could not send the message from client, status Bad\n");
+	}
+	if(status==Ok)
+	{
+		int i=1;
+		while(i<4)
+		{
+			if(anyThingThere(s)==Bad) 
+			{
+				//no available socket fd, status bad, send message again
+				status=Bad;
+				printf("Sending message again\n");
+				UDPsend(s, message, serverSA);
+			}
+			else
+			{
+				status=Ok;
+				//socket fd available, receives the message from server
+				if((status= UDPreceive(s, reply, &serverSA)) == Ok)
+				{
+					printf("Message received from server: %s\n", reply->data);
+				}
+				else
+				{
+					printf("No message received from server\n");
+					status=Bad;
+				}
+				break;
+			}
+			i++;				
+		}
+		
+	}
+	if(status==Bad) // socket fd not available after checking 3 times also. Client program displays message and exits
+	{	
+		printf("Timeout, no response from server. Exiting client..\n");
+		exit(1);
+	}	return status;	
+}
+
+
+// use select to test whether there is any input on descriptor
+Status anyThingThere(int s)
+{
+	Status timeoutstatus=Ok;
+	fd_set rfds;
+	struct timeval timeout;
+	int n;
+	FD_ZERO(&rfds);
+        FD_SET(s, &rfds);
+	timeout.tv_sec =3; /*seconds wait*/
+	timeout.tv_usec = 0;        /* micro seconds*/
+	if((n = select(s+1, &rfds, 0, 0, &timeout))<0)
+		perror("Select fail:\n");
+	else if(!n)
+	{
+		timeoutstatus=Bad;
+	}
+	return timeoutstatus;		
+}
+
+/* sends a given message through a socket to a given socket address and returns status*/
+Status UDPsend(int s, Message *m, SocketAddress destination)
+{
+	Status status;int n;
+	if( (n = sendto(s, m, sizeof(Message), 0, (struct sockaddr *)&destination, sizeof(destination))) > 0)
+	{
+		status=Ok;
+	}		
+	else 
+	{
+
+		printf("UDPsend: Could not send reply back to client, Status is bad\n");
+		status=Bad;
+	}
+	return status;
+}
+
+/*receives a message and the socket address of the sender and returns status*/
+Status UDPreceive(int s, Message *m, SocketAddress *origin)
+{
+	Status status;
+	int addrlen=sizeof(SocketAddress);
+	int n=0;
+	if((n = recvfrom(s, m,  sizeof(Message), 0, (struct sockaddr *)origin, &addrlen)) > 0) 
+	{
+		status=Ok;
+	}
+	else
+	{
+		printf("UDP Receive: Status is bad\n");
+		status=Bad;
+	} 
+	return status;
+}
+
+
+
+/* make a socket address using any of the addressses of this computer
+for a local socket on any port */
+void makeLocalSA(SocketAddress *sa)
+{
+	sa->sin_family = AF_INET;
+	sa->sin_port = htons(0);
+	sa-> sin_addr.s_addr = htonl(INADDR_ANY);
+}
+
+
+/*print a socket address */
+void printSA(SocketAddress sa)
+{
+	char mybuf[80];
+	inet_ntop(AF_INET, &sa.sin_addr, mybuf, 80);
+	printf("sa = %d, %s, %d\n", sa.sin_family, mybuf, ntohs(sa.sin_port));
+}
+
+
+/* make a socket address for a destination whose machine and port are given as arguments */
+void makeDestSA(SocketAddress * sa, char *hostname, int port)
+{
+	struct hostent *host;
+
+	sa->sin_family = AF_INET;
+	if((host = gethostbyname(hostname))== NULL){
+		printf("Unknown host name\n");
+		exit(-1);
+	}
+	sa-> sin_addr = *(struct in_addr *) (host->h_addr);
+	sa->sin_port = htons(port);
+}
+
+
+