Send more information with the stream open tag

smack-core/src/main/java/org/jivesoftware/smack/packet/StreamOpen.java

@@ -17,6 +17,7 @@
 
 package org.jivesoftware.smack.packet;
 
+import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 /**
@@ -59,13 +60,17 @@ public class StreamOpen extends FullStreamElement {
      */
     private final String contentNamespace;
 
-    public StreamOpen(String to) {
+    public StreamOpen(CharSequence to) {
        this(to, null, null, null, StreamContentNamespace.client);
     }
 
-    public StreamOpen(String to, String from, String id, String lang, StreamContentNamespace ns) {
+    public StreamOpen(CharSequence to, CharSequence from, String id) {
-        this.to = to;
+        this(to, from, id, "en", StreamContentNamespace.client);
-        this.from = from;
+    }
+
+    public StreamOpen(CharSequence to, CharSequence from, String id, String lang, StreamContentNamespace ns) {
+        this.to = StringUtils.maybeToString(to);
+        this.from = StringUtils.maybeToString(from);
         this.id = id;
         this.lang = lang;
         switch (ns) {

smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java

@@ -264,4 +264,17 @@ public class StringUtils {
         }
         return cs;
     }
+
+    /**
+     * Return the String representation of the given char sequence if it is not null.
+     *
+     * @param cs the char sequence or null.
+     * @return the String representation of <code>cs</code> or null.
+     */
+    public static String maybeToString(CharSequence cs) {
+        if (cs == null) {
+            return null;
+        }
+        return cs.toString();
+    }
 }

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -74,6 +74,7 @@ import org.jivesoftware.smack.util.PacketParserUtils;
 import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.TLSUtils;
 import org.jivesoftware.smack.util.dns.HostAddress;
+import org.jxmpp.util.XmppStringUtils;
 import org.xmlpull.v1.XmlPullParser;
 import org.xmlpull.v1.XmlPullParserException;
 
@@ -882,7 +883,18 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
      * @throws SmackException if the parser could not be reset.
      */
     void openStream() throws SmackException {
-        send(new StreamOpen(getServiceName()));
+        // If possible, provide the receiving entity of the stream open tag, i.e. the server, as much information as
+        // possible. The 'to' attribute is *always* available. The 'from' attribute if set by the user and no external
+        // mechanism is used to determine the local entity (user). And the 'id' attribute is available after the first
+        // response from the server (see e.g. RFC 6120 § 9.1.1 Step 2.)
+        CharSequence to = getServiceName();
+        CharSequence from = null;
+        CharSequence localpart = config.getUsername();
+        if (localpart != null) {
+            from = XmppStringUtils.completeJidFrom(localpart, to);
+        }
+        String id = getConnectionID();
+        send(new StreamOpen(to, from, id));
         try {
             packetReader.parser = PacketParserUtils.newXmppParser(reader);
         }