From 84956cdcdbf68a1f8c8af802aecf1c2f43e69e39 Mon Sep 17 00:00:00 2001
From: Christopher Bohn <bohn@unl.edu>
Date: Tue, 5 Nov 2019 13:09:49 -0600
Subject: [PATCH] Application recovers if IP address has a malformed octet
- Handles octet that is out of range of legal signed byte values
- Handles octet that isn't a number
Partially addresses #7
---
.../edu/unl/cse/csce361/socket_chat/Chat.java | 51 ++++++++++++++-----
1 file changed, 39 insertions(+), 12 deletions(-)
diff --git a/src/main/java/edu/unl/cse/csce361/socket_chat/Chat.java b/src/main/java/edu/unl/cse/csce361/socket_chat/Chat.java
index e655ac2..3bbebe1 100644
--- a/src/main/java/edu/unl/cse/csce361/socket_chat/Chat.java
+++ b/src/main/java/edu/unl/cse/csce361/socket_chat/Chat.java
@@ -66,34 +66,61 @@ public class Chat {
byte[] address = InetAddress.getLocalHost().getAddress();
System.out.println("Host address: " + address[0] + "." + address[1] + "." + address[2] + "." + address[3]);
String prompt = "Select port number";
- short port = getPort(prompt);
+ int port = getPort(prompt);
ServerSocket serverSocket = new ServerSocket(port);
return serverSocket.accept();
}
private Socket connectAsClient() throws IOException {
- System.out.print("Enter IP address of host <##.##.##.##>: ");
- String addressString = scanner.nextLine();
- String[] tokens = addressString.split("\\.");
- byte[] address = new byte[4];
- for (int i = 0; i < 4; i++) {
- address[i] = Byte.parseByte(tokens[i]);
- }
+ byte[] address = getRemoteHostAddress();
String prompt = "Enter port host is opening at " +
address[0] + "." + address[1] + "." + address[2] + "." + address[3];
- short port = getPort(prompt);
+ int port = getPort(prompt);
return new Socket(InetAddress.getByAddress(address), port);
}
- private short getPort(String prompt) {
+ private byte[] getRemoteHostAddress() {
+ // This assumes IPv4. Probably a good assumption.
+ boolean haveGoodAddress = false;
+ byte[] address = new byte[4];
+ while (!haveGoodAddress) {
+ System.out.print("Enter IP address of host <##.##.##.##>: ");
+ haveGoodAddress = true;
+ try {
+ String addressString = scanner.nextLine();
+ String[] tokens = addressString.split("\\.");
+ for (int i = 0; i < 4; i++) {
+ address[i] = Byte.parseByte(tokens[i]);
+ }
+ } catch (NumberFormatException nfException) {
+ System.out.println("The IP address should be exactly as reported to the host user.");
+ String message = nfException.getMessage();
+ if (message.startsWith("Value out of range. Value")) {
+ String[] messageTokens = message.split("\"");
+ long value = Long.parseLong(messageTokens[1]); // this is fragile to an unexpected message format
+ if ((127 < value) && (value < 256)) {
+ System.out.println("Note that Java does not have unsigned integers, so subtract 256 from " +
+ "values greater than 127. For example, " + value + " should be " + (value - 256) + ".");
+ }
+ }
+ haveGoodAddress = false;
+ }
+ }
+ return address;
+ }
+
+ private int getPort(String prompt) {
boolean haveGoodNumber = false;
- short port = 0;
+ int port = 0;
while (!haveGoodNumber) {
System.out.print(prompt + ": ");
haveGoodNumber = true;
try {
- port = scanner.nextShort();
+ port = scanner.nextInt();
if (port < 0) throw new InputMismatchException("Expected non-negative value, got " + port);
+ if (port >= 2 * (Short.MAX_VALUE + 1)) {
+ throw new InputMismatchException("Expected value less than 65536, got " + port);
+ }
} catch (InputMismatchException ignored) {
System.out.println("The port number must be a positive integer strictly less than 65536.");
haveGoodNumber = false;
--
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