added support for dropp current client - needs a separate thread to remove blocking

client.c

@@ -83,45 +83,66 @@ int client_write(struct client_t *client, char *databuf, int datalen) {
 	return len;
 }
 
+/* Waits for client input in "line mode". Blocks until input arrives. */
+int client_wait_line(struct client_t *client) {
+	
+	int ret;
+	fd_set read_fds;
+	
+	client->data[0] = '\0';
+	/* loop waiting for client input */
+	while (client->data[0] == '\0') {
+		/* setup select() parameters */
+		FD_ZERO(&read_fds);
+		FD_SET(client->socket, &read_fds);
+		/* send prompt character to client */
+		client_write(client, "> ", 2);
+		/* block until input arrives */
+		if (select((client->socket)+1, &read_fds, NULL, NULL, NULL) == -1) return -1;
+		if (FD_ISSET(client->socket, &read_fds)) {
+			/* read client input */
+			ret = client_read(client);
+			if (ret == -1) return -1;
+			/* we don't want empty data so stop on \r or \n */
+			if ( (client->data[0] == '\r') || (client->data[0] == '\n') ) {
+				fprintf(stderr, "client data is empty\n");
+				client->data[0] = '\0';
+			}
+		}
+	}
+	
+	fprintf(stderr, "client data: %s\n", client->data);
+	return 0;
+}
+
 /* Waits for client to provide a username. Blocks until a username is entered. */
 int client_ask_username(struct client_t *client) {
 	
 	int i;
-	char databuf[DATABUF_LEN];
+	char msg[DATABUF_LEN];
-	fd_set read_fds;
 	
 	/* send username request to client */
-	snprintf(databuf, DATABUF_LEN,
+	snprintf(msg, DATABUF_LEN,
 			 "\nPlease provide a username to identify yourself to other users (max %d characters):\n", USERNAME_LEN);
-	client_write(client, databuf, strlen(databuf));
+	client_write(client, msg, strlen(msg));
 	
 	/* wait for client input */
-	client->username[0] = '\0';
+	if (client_wait_line(client) != 0) return -1;
-	while (client->username[0] == '\0') {
+	
-		/* send prompt character to client */
+	/* save received data as client username */
-		snprintf(databuf, DATABUF_LEN, "> ");
-		client_write(client, databuf, strlen(databuf));
-		/* setup select() parameters */
-		FD_ZERO(&read_fds);
-		FD_SET(client->socket, &read_fds);
-		select((client->socket)+1, &read_fds, NULL, NULL, NULL);
-		if (FD_ISSET(client->socket, &read_fds)) {
-			client_read(client);
-			/* handle client input */
 	for (i = 0; i < USERNAME_LEN; i++) {
-				if (client->data[i] == '\r') {
+		if ( (client->data[i] == '\r') || (client->data[i] == '\n') ) {
+			/* don't include \r or \n in username */
+			client->username[i] = '\0';
 			break;
 		}
 		client->username[i] = client->data[i];
 	}
-			client->username[i+1] = '\0';
-		}
-	}
 	
 	/* send welcome message to client */
-	snprintf(databuf, DATABUF_LEN,
+	snprintf(msg, DATABUF_LEN,
 			 "\nWelcome %s!\n\n", client->username);
-	client_write(client, databuf, strlen(databuf));
+	client_write(client, msg, strlen(msg));
 	
 	return 0;
 }

moxerver.c

@@ -215,9 +215,22 @@ int main(int argc, char *argv[]) {
 					/* put client in "character" mode */
 					telnet_set_character_mode(&client);
 				}
-				/* reject connection request if a client is already connected */
+				/* if a client is already connected then new clients need to be handled */
 				else {
-					server_reject(&server, &client);
+					/* decide if current client needs to be dropped or new client needs to be rejected */
+					ret = server_drop(&server, &client);
+					if (ret < 0) {
+						/* error in handling new clients, print but continue waiting for new clients */
+						fprintf(stderr, "[%s] problem handling new client request\n", NAME);
+						continue;
+					}
+					/* if current client was dropped we need to set up new client */
+					if (ret > 0) {
+						/* ask client to provide a username before going to "character" mode */
+						client_ask_username(&client);
+						/* put client in "character" mode */
+						telnet_set_character_mode(&client);
+					}
 				}
 			}
 			/* check client status if connected */

moxerver.h

@@ -91,12 +91,15 @@ int server_close(struct server_t *server);
 int server_accept(struct server_t *server, struct client_t *accepted_client);
 
 /**
- * Rejects incoming client connection.
+ * Asks new incoming client connection if current client needs to be dropped.
+ * If current client doesn't need to be dropped then new client is rejected.
  * 
  * Returns:
- * 0 always, errors with rejected client are ignored
+ * - positive value if current client was dropped 
+ * - 0 if new client was rejected
+ * - negative value if error occurred
  */
-int server_reject(struct server_t *server, struct client_t *client);
+int server_drop(struct server_t *server, struct client_t *client);
 
 
 /* Functions handling communication with clients. */
@@ -129,12 +132,23 @@ int client_read(struct client_t *client);
  */
 int client_write(struct client_t *client, char *databuf, int datalen);
 
+/**
+ * Waits for client input in "line mode", where client sends a whole line of characters.
+ * Blocks until input arrives.
+ * 
+ * Returns:
+ * - 0 on success
+ * - negative value if error occurred
+ */
+int client_wait_line(struct client_t *client);
+
 /**
  * Waits for client to provide a username.
  * Blocks until a username is entered.
  *
  * Returns:
- * 0 always
+ * - 0 on success
+ * - negative value if error occurred
  */
 int client_ask_username(struct client_t *client);
 

server.c

@@ -103,26 +103,53 @@ int server_accept(struct server_t *server, struct client_t *accepted_client) {
 	return 0;
 }
 
-/* Rejects incoming client connection. Errors with rejected client are ignored. */
+/* Drops current client or rejects new client. */
-int server_reject(struct server_t *server, struct client_t *client) {
+int server_drop(struct server_t *server, struct client_t *current_client) {
 	
-	int namelen;
+	struct client_t new_client;
-	struct client_t rclient;
+	char msg[DATABUF_LEN];
-	char reject_msg[128];
 	char timestamp[TIMESTAMP_LEN];
 	
-	/* accept connection request */
+	/* accept new connection request */
-	namelen = sizeof(rclient.address);
+	if (server_accept(server, &new_client) != 0) return -1;
-	rclient.socket = accept(server->socket, (struct sockaddr *) &rclient.address, (socklen_t *) &namelen);
-	/* send reject message to client */
-	time2string(client->last_active, timestamp);
-	sprintf(reject_msg, "\nPort %u is already being used:\ncurrent user: %s\nlast activity: @ %s\n\n",
-			server->port, client->username, timestamp);
-	send(rclient.socket, reject_msg, strlen(reject_msg), 0);
-	/* close connection */
-	close(rclient.socket);
 	
+	/* inform new client that port is already in use */
+	time2string(current_client->last_active, timestamp);
+	sprintf(msg, "\nPort %u is already being used!\nCurrent user and last activity:\n%s @ %s\n",
+			server->port, current_client->username, timestamp);
+	send(new_client.socket, msg, strlen(msg), 0);
+	
+	/* ask new client if current client should be dropped */
+	sprintf(msg, "\nDo you want to drop the current user?\nIf yes then please type YES DROP (in uppercase):");
+	send(new_client.socket, msg, strlen(msg), 0);
+	
+	/* wait for client input */
+	if (client_wait_line(&new_client) != 0) return -1;
+	
+	/* check client confirmation */
+	if (strncmp(new_client.data, "YES DROP", 8) == 0) {
+		/* current client should be dropped, drop it */
+		client_close(current_client);
 		time2string(time(NULL), timestamp);
-	fprintf(stderr, "[%s] rejected new client request @ %s\n", __func__, timestamp);
+		fprintf(stderr, "[%s] dropped current client %s on port %u @ %s\n", __func__,
+				current_client->ip_string, server->port, timestamp);
+		/* make new client the current client */
+		memcpy(current_client, &new_client, sizeof(struct client_t));
+		time2string(time(NULL), timestamp);
+		fprintf(stderr, "[%s] accepted new client request %s on port %u @ %s\n", __func__,
+				current_client->ip_string, server->port, timestamp);
+		/* return 1 because current client was dropped */
+		return 1;
+	}
+	else {
+		/* new connection should be rejected, close connection */
+		close(new_client.socket);
+		time2string(time(NULL), timestamp);
+		fprintf(stderr, "[%s] rejected new client request %s on port %u @ %s\n", __func__,
+				new_client.ip_string, server->port, timestamp);
+		/* return 0 because new client was rejected */
 		return 0;
+	}
+	
+	
 }