Unix Domain Socket

AF_UNIX/server.c

@@ -0,0 +1,178 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+
+#define SOCKET_NAME "/tmp/DemoSocket" /* Unique name of the socket */
+#define BUFFER_SIZE 128				  /* Size of the buffer which will be used by
+										for Communication. */
+
+int
+main(int argc, char* argv[]) {
+
+	/* Structure provided by Unix library for using
+		it as an identifier for managing the socket */
+
+	struct sockaddr_un name;
+
+#if 0
+	
+	struct sockaddr_un {
+
+		/* This member describe what type of data it
+			will handle. Define the family of the 
+			socket. Here, we are using UNIX DOMAIN socket
+			so AF_UNIX constant should be used for
+			classification. */
+		sa_family_t sun_family;			/* AF_UNIX */
+
+		/* Hold the name of the socket with the path where it
+			is created. */
+		char sun_path[108];				/* pathname */
+	};
+#endif
+
+	int ret;
+	int connection_socket;
+	int data_socket;
+	int result;
+	int data;
+	char buffer[BUFFER_SIZE];
+
+	/* In case the program exited inadvertently on the last run, 
+		remove the socket. */
+
+
+	unlink(SOCKET_NAME);
+
+	/* Create Master socket */
+
+	/* SOCK_DGRAM for Datagram based communication */
+	connection_socket = socket(AF_UNIX, SOCK_STREAM, 0);
+
+	if (connection_socket == -1) {
+
+		perror("socket");
+		exit(EXIT_FAILURE);
+
+	}
+
+	printf("Master socket created\n");
+
+	/* initialize */
+	memset(&name, 0, sizeof(struct sockaddr_un));
+
+	/* Specify the socket Cridentials */
+	name.sun_family = AF_UNIX;
+	strncpy(name.sun_path, SOCKET_NAME, sizeof(name.sun_path) - 1);
+
+	/* Bind Socket to socket name. */
+	/* Purpose of bind() system call is that application() dictate the underlying
+	   operating system the criteria of receiving the data. Here, bind() system call
+	   is telling the OS that if sender process sends the data destined to socket 
+	   "tmp/DemoSocket", then such data needs to be delievered to this server process
+	   ( the server process ) */
+
+	ret = bind(connection_socket, (const struct sockaddr* )&name,
+		sizeof(struct sockaddr_un));
+
+	if (ret == -1) {
+		perror("bind");
+		exit(EXIT_FAILURE);
+	}
+
+
+	printf("bind() call succeed\n");
+
+	/* Prepare for accepting connections. The backlog size is set to 20.
+	   So, while one request is being processed other requests can be 
+	   waiting.
+	   */
+
+	ret = listen(connection_socket, 20);
+
+	if (ret == -1) {
+		perror("listen");
+		exit(EXIT_FAILURE);
+	}
+
+	/* This is the main loop for handling connections. */
+	/* All Server process usually runs 24 x 7. Good Servers should always up 
+	   running and should never go down. */
+
+	for (;;) {
+
+		/* Wait for incoming connection. */
+
+		printf("Waiting on accept() sys call\n");
+
+		data_socket = accept(connection_socket, NULL, NULL);
+
+		if (data_socket == -1) {
+			perror("accept");
+			exit(EXIT_FAILURE);
+		}
+
+		printf("Connection accepted from client\n");
+
+		result = 0;
+		for (;;) {
+
+			/* Prepare the buffer to recv the data*/
+			memset(buffer, 0, BUFFER_SIZE);
+
+			/*Wait for next data packet. */
+			/* Server is blocked here. Waiting for the data to arrive from client
+			   'read' is a blocking system call.  */
+			printf("Waiting for data from the client\n");
+
+			ret = read(data_socket, buffer, BUFFER_SIZE);
+
+			if (ret == -1) {
+				perror("read");
+				exit(EXIT_FAILURE);
+			}
+
+			/* Add received summand */
+
+			memcpy(&data, buffer, sizeof(int));
+			if (data == 0) break;
+			result += data;
+
+		}
+
+		/* Send result. */
+		memset(buffer, 0, BUFFER_SIZE);
+		sprintf(buffer, "Result = %d", result);
+
+
+		printf("Sending final result back to client\n");
+
+		/* non-blockding system call */
+		ret = write(data_socket, buffer, BUFFER_SIZE);
+		if (ret == -1) {
+			perror("write");
+			exit(EXIT_FAILURE);
+		}
+
+		/*close socket*/
+		close(data_socket);
+
+
+	}
+	
+	/*close the master socket*/
+	close(connection_socket);
+	printf("connection closed..\n");
+
+	/* Server should release resources before getting terminated.
+		Unlink the socket. */
+
+	unlink(SOCKET_NAME);
+	exit(EXIT_SUCCESS);
+	return 0;
+}
+