首先看飞鸽传书和飞秋是什么：它们是局域网内聊天或者是传输文件的工作，类似于QQ，但是它们作用于局域网，不需要服务器。
那么，既然没有服务器，我们怎么去拿到好友列表呢？？类似于QQ这样的聊天工具，我们注册了账号，添加了好友，好友信息都在服务器，一旦登录了该账号，我们便可以到服务器把相关的信息拿下来，但是我们的飞鸽传书和飞秋是没有服务器的，那怎么拿到好友列表呢？
我们不妨这么做：
首先当我们进入到应用的时候，我们使用udp发送一个 "255.255.255.255" 的广播，通知到所有局域网内的已经登录的用户，我已经登录了。那已经登录过的终端便可以得到新上线客户端的登录信息。
然后当已经登录的终端接收到了广播之后，给发送通知的客户端一个消息作为应答，新登录机子在收到应答后马上将给应答包的机子添加到列表中，这样就获取到了好友的列表。
下面我画一个简图说明一下：
当然这个过程搞明白就狠清除，很简单了，不过虽然过程在脑子里是很清楚了，实现起来却也并不是那么的容易
android的简单页面搭建部分的我就不再赘述了，相信这个大家写起来都没有问题的
下面想一想，要实现这玩意儿是用什么协议？http？肯定是不行了，tcp 或者 udp吧，这里我选择了udp协议，原因是它只管发送不去管对方是否接收到，也确保了消息的时效性，不需要进行去三次握手啊等等的步骤，当然你要说 tcp比udp更安全，好吧，我承认，但是在局域网内，我相信网络是狠OK的，如果你持有不同意见，咱们再议。
udp传输数据更快，它不去进行校验，不去进行握手等等，所以我选择udp。
选定了协议，那么就去实现这个协议吧：我下面把我实现协议部分贴上来
import java.util.Date;
/**
* IPMSG协议抽象类
* IPMSG协议格式：
* Ver(1): PacketNo:SenderName:SenderHost:CommandNo:AdditionalSection
* 每部分分别对应为：版本号（现在是1）:数据包编号:发送主机:命令:附加数据
* 其中：
* 数据包编号，一般是取毫秒数。利用这个数据，可以唯一的区别每个数据包；
* SenderName指的是发送者的昵称(实际上是计算机登录名)
* 发送主机，指的是发送主机的主机名；（主机名）
* 命令，指的是飞鸽协议中定义的一系列命令，具体见下文；
* 附加数据，指的是对应不同的具体命令，需要提供的数据。当为上线报文时，附加信息内容是用户名和分组名，中间用"\0"分隔
*
* 例如：
* 1:100:shirouzu:jupiter:32:Hello
* 表示 shirouzu用户发送了 Hello 这条消息（32对应为IPMSG_SEND_MSG这个命令，具体需要看源码中的宏定义）。
*/
public class IpMessageProtocol {
private String version; //版本号 目前都为1
private String packetNo;//数据包编号
private String senderName; //发送者昵称
private String senderHost; //发送主机名
private int commandNo; //命令
private String additionalSection; //附加数据
public IpMessageProtocol(){
this.packetNo = getSeconds();
}
// 根据协议字符串初始化
public IpMessageProtocol(String protocolString){
String[] args = protocolString.split(":"); // 以:分割协议串
version = args[0];
packetNo = args[1];
senderName = args[2];
senderHost = args[3];
commandNo = Integer.parseInt(args[4]);
if(args.length >= 6){ //是否有附加数据
additionalSection = args[5];
}else{
additionalSection = "";
}
for(int i = 6; i < args.length; i++){ //处理附加数据中有:的情况
additionalSection += (":" + args[i]);
}
}
public IpMessageProtocol(
String senderName, String senderHost, int commandNo,
String additionalSection) {
super();
this.version = "1";
this.packetNo = getSeconds();
this.senderName = senderName;
this.senderHost = senderHost;
this.commandNo = commandNo;
this.additionalSection = additionalSection;
}
public String getVersion() {
return version;
}
public void setVersion(String version) {
this.version = version;
}
public String getPacketNo() {
return packetNo;
}
public void setPacketNo(String packetNo) {
this.packetNo = packetNo;
}
public String getSenderName() {
return senderName;
}
public void setSenderName(String senderName) {
this.senderName = senderName;
}
public String getSenderHost() {
return senderHost;
}
public void setSenderHost(String senderHost) {
this.senderHost = senderHost;
}
public int getCommandNo() {
return commandNo;
}
public void setCommandNo(int commandNo) {
this.commandNo = commandNo;
}
public String getAdditionalSection() {
return additionalSection;
}
public void setAdditionalSection(String additionalSection) {
this.additionalSection = additionalSection;
}
//得到协议串
public String getProtocolString(){
StringBuffer sb = new StringBuffer();
sb.append(version);
sb.append(":");
sb.append(packetNo);
sb.append(":");
sb.append(senderName);
sb.append(":");
sb.append(senderHost);
sb.append(":");
sb.append(commandNo);
sb.append(":");
sb.append(additionalSection);
return sb.toString();
}
//得到数据包编号，毫秒数
private String getSeconds(){
Date nowDate = new Date();
return Long.toString(nowDate.getTime());
}
}
这个是udp协议，参考了一份代码，作者是谁忘了，见谅：
那接下来我们就是发送广播消息接受消息了：
public void noticeOnline(){ // 发送上线广播
IpMessageProtocol ipmsgSend = new IpMessageProtocol();
ipmsgSend.setVersion(String.valueOf(IpMessageConst.VERSION));
ipmsgSend.setSenderName(selfName);
ipmsgSend.setSenderHost(selfGroup);
ipmsgSend.setCommandNo(IpMessageConst.IPMSG_BR_ENTRY); //上线命令
ipmsgSend.setAdditionalSection(selfName + "\0" ); //附加信息里加入用户名和分组信息
InetAddress broadcastAddr;
try {
broadcastAddr = InetAddress.getByName("255.255.255.255"); //广播地址
sendUdpData(ipmsgSend.getProtocolString()+"\0", broadcastAddr, IpMessageConst.PORT); //发送数据
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e(TAG, "noticeOnline()....广播地址有误");
}
}
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.net;
import java.io.FileDescriptor;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamException;
import java.io.ObjectStreamField;
import java.io.Serializable;
import java.security.AccessController;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.StringTokenizer;
import org.apache.harmony.luni.net.NetUtil;
import org.apache.harmony.luni.platform.INetworkSystem;
import org.apache.harmony.luni.platform.Platform;
import org.apache.harmony.luni.util.Inet6Util;
import org.apache.harmony.luni.util.Msg;
import org.apache.harmony.luni.util.PriviAction;
/**
* An Internet Protocol (IP) address. This can be either an IPv4 address or an IPv6 address, and
* in practice you‘ll have an instance of either {@code Inet4Address} or {@code Inet6Address} (this
* class cannot be instantiated directly). Most code does not need to distinguish between the two
* families, and should use {@code InetAddress}.
* <p>
* An {@code InetAddress} may have a hostname (accessible via {@code getHostName}), but may not,
* depending on how the {@code InetAddress} was created.
* <p>
* On Android, addresses are cached for 600 seconds (10 minutes) by default. Failed lookups are
* cached for 10 seconds. The underlying C library or OS may cache for longer, but you can control
* the Java-level caching with the usual {@code "networkaddress.cache.ttl"} and
* {@code "networkaddress.cache.negative.ttl"} system properties. These are parsed as integer
* numbers of seconds, where the special value 0 means "don‘t cache" and -1 means "cache forever".
* <p>
* Note also that on Android – unlike the RI – the cache is not unbounded. The current
* implementation caches around 512 entries, removed on a least-recently-used basis.
* (Obviously, you should not rely on these details.)
*
* @see Inet4Address
* @see Inet6Address
*/
public class InetAddress implements Serializable {
// BEGIN android-added: better DNS caching.
// Our Java-side DNS cache.
private static final AddressCache addressCache = new AddressCache();
// END android-added
private final static INetworkSystem NETIMPL = Platform.getNetworkSystem();
private static final String ERRMSG_CONNECTION_REFUSED = "Connection refused"; //$NON-NLS-1$
private static final long serialVersionUID = 3286316764910316507L;
String hostName;
private static class WaitReachable {
}
private transient Object waitReachable = new WaitReachable();
private boolean reached;
private int addrCount;
int family = 0;
static final int AF_INET = 2;
static final int AF_INET6 = 10;
byte[] ipaddress;
// BEGIN android-removed
// // Fill in the JNI id caches
// private static native void oneTimeInitialization(boolean supportsIPv6);
//
// static {
// oneTimeInitialization(true);
// }
// END android-removed
/**
* Constructs an {@code InetAddress}.
*
* Note: this constructor should not be used. Creating an InetAddress
* without specifying whether it‘s an IPv4 or IPv6 address does not make
* sense, because subsequent code cannot know which of of the subclasses‘
* methods need to be called to implement a given InetAddress method. The
* proper way to create an InetAddress is to call new Inet4Address or
* Inet6Address or to use one of the static methods that return
* InetAddresses (e.g., getByAddress). That is why the API does not have
* public constructors for any of these classes.
*/
InetAddress() {
super();
}
// BEGIN android-removed
/**
* Constructs an {@code InetAddress}, representing the {@code address} and
* {@code hostName}.
*
* @param address
* the network address.
*/
// InetAddress(byte[] address) {
// super();
// this.ipaddress = address;
// }
// END android-removed
// BEGIN android-removed
/**
* Constructs an {@code InetAddress}, representing the {@code address} and
* {@code hostName}.
*
* @param address
* the network address.
*
*/
// InetAddress(byte[] address, String hostName) {
// super();
// this.ipaddress = address;
// this.hostName = hostName;
// }
// END android-removed
// BEGIN android-removed
// CacheElement cacheElement() {
// return new CacheElement();
// }
// END android-removed
/**
* Compares this {@code InetAddress} instance against the specified address
* in {@code obj}. Two addresses are equal if their address byte arrays have
* the same length and if the bytes in the arrays are equal.
*
* @param obj
* the object to be tested for equality.
* @return {@code true} if both objects are equal, {@code false} otherwise.
*/
@Override
public boolean equals(Object obj) {
// BEGIN android-changed
if (!(obj instanceof InetAddress)) {
return false;
}
return Arrays.equals(this.ipaddress, ((InetAddress) obj).ipaddress);
// END android-changed
}
/**
* Returns the IP address represented by this {@code InetAddress} instance
* as a byte array. The elements are in network order (the highest order
* address byte is in the zeroth element).
*
* @return the address in form of a byte array.
*/
public byte[] getAddress() {
return ipaddress.clone();
}
// BEGIN android-added
static final Comparator<byte[]> SHORTEST_FIRST = new Comparator<byte[]>() {
public int compare(byte[] a1, byte[] a2) {
return a1.length - a2.length;
}
};
/**
* Converts an array of byte arrays representing raw IP addresses of a host
* to an array of InetAddress objects, sorting to respect the value of the
* system property {@code "java.net.preferIPv6Addresses"}.
*
* @param rawAddresses the raw addresses to convert.
* @param hostName the hostname corresponding to the IP address.
* @return the corresponding InetAddresses, appropriately sorted.
*/
static InetAddress[] bytesToInetAddresses(byte[][] rawAddresses,
String hostName) {
// If we prefer IPv4, ignore the RFC3484 ordering we get from getaddrinfo
// and always put IPv4 addresses first. Arrays.sort() is stable, so the
// internal ordering will not be changed.
if (!NetUtil.preferIPv6Addresses()) {
Arrays.sort(rawAddresses, SHORTEST_FIRST);
}
// Convert the byte arrays to InetAddresses.
InetAddress[] returnedAddresses = new InetAddress[rawAddresses.length];
for (int i = 0; i < rawAddresses.length; i++) {
byte[] rawAddress = rawAddresses[i];
if (rawAddress.length == 16) {
returnedAddresses[i] = new Inet6Address(rawAddress, hostName);
} else if (rawAddress.length == 4) {
returnedAddresses[i] = new Inet4Address(rawAddress, hostName);
} else {
// Cannot happen, because the underlying code only returns
// addresses that are 4 or 16 bytes long.
throw new AssertionError("Impossible address length " +
rawAddress.length);
}
}
return returnedAddresses;
}
// END android-added
/**
* Gets all IP addresses associated with the given {@code host} identified
* by name or literal IP address. The IP address is resolved by the
* configured name service. If the host name is empty or {@code null} an
* {@code UnknownHostException} is thrown. If the host name is a literal IP
* address string an array with the corresponding single {@code InetAddress}
* is returned.
*
* @param host the hostname or literal IP string to be resolved.
* @return the array of addresses associated with the specified host.
* @throws UnknownHostException if the address lookup fails.
*/
public static InetAddress[] getAllByName(String host)
throws UnknownHostException {
// BEGIN android-changed
return getAllByNameImpl(host, true);
// END android-changed
}
// BEGIN android-added
/**
* Implementation of getAllByName.
*
* @param host the hostname or literal IP string to be resolved.
* @param returnUnshared requests a result that is modifiable by the caller.
* @return the array of addresses associated with the specified host.
* @throws UnknownHostException if the address lookup fails.
*/
static InetAddress[] getAllByNameImpl(String host, boolean returnUnshared)
throws UnknownHostException {
if (host == null || 0 == host.length()) {
if (NetUtil.preferIPv6Addresses()) {
return new InetAddress[] { Inet6Address.LOOPBACK,
Inet4Address.LOOPBACK };
} else {
return new InetAddress[] { Inet4Address.LOOPBACK,
Inet6Address.LOOPBACK };
}
}
// Special-case "0" for legacy IPv4 applications.
if (host.equals("0")) { //$NON-NLS-1$
return new InetAddress[] { Inet4Address.ANY };
}
if (isHostName(host)) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkConnect(host, -1);
}
if (returnUnshared) {
return lookupHostByName(host).clone();
} else {
return lookupHostByName(host);
}
}
byte[] hBytes = NETIMPL.ipStringToByteArray(host);
if (hBytes.length == 4) {
return (new InetAddress[] { new Inet4Address(hBytes) });
} else if (hBytes.length == 16) {
return (new InetAddress[] { new Inet6Address(hBytes) });
} else {
throw new UnknownHostException(
Msg.getString("K0339")); //$NON-NLS-1$
}
}
// END android-added
/**
* Returns the address of a host according to the given host string name
* {@code host}. The host string may be either a machine name or a dotted
* string IP address. If the latter, the {@code hostName} field is
* determined upon demand. {@code host} can be {@code null} which means that
* an address of the loopback interface is returned.
*
* @param host
* the hostName to be resolved to an address or {@code null}.
* @return the {@code InetAddress} instance representing the host.
* @throws UnknownHostException
* if the address lookup fails.
*/
public static InetAddress getByName(String host) throws UnknownHostException {
return getAllByNameImpl(host, false)[0];
}
// BEGIN android-added
/**
* Returns the numeric string form of the given IP address.
*
* @param ipAddress
* the byte array to convert; length 4 for IPv4, 16 for IPv6.
* @throws IllegalArgumentException
* if ipAddress is of length other than 4 or 16.
*/
private static String ipAddressToString(byte[] ipAddress) {
try {
return NETIMPL.byteArrayToIpString(ipAddress);
} catch (IOException ex) {
throw new IllegalArgumentException("byte[] neither 4 nor 16 bytes", ex);
}
}
// END android-added
/**
* Gets the textual representation of this IP address.
*
* @return the textual representation of host‘s IP address.
*/
public String getHostAddress() {
return ipAddressToString(ipaddress);
}
/**
* Gets the host name of this IP address. If the IP address could not be
* resolved, the textual representation in a dotted-quad-notation is
* returned.
*
* @return the corresponding string name of this IP address.
*/
public String getHostName() {
try {
if (hostName == null) {
int address = 0;
if (ipaddress.length == 4) {
address = bytesToInt(ipaddress, 0);
if (address == 0) {
return hostName = ipAddressToString(ipaddress);
}
}
hostName = getHostByAddrImpl(ipaddress).hostName;
if (hostName.equals("localhost") && ipaddress.length == 4 //$NON-NLS-1$
&& address != 0x7f000001) {
return hostName = ipAddressToString(ipaddress);
}
}
} catch (UnknownHostException e) {
return hostName = ipAddressToString(ipaddress);
}
SecurityManager security = System.getSecurityManager();
try {
// Only check host names, not addresses
if (security != null && isHostName(hostName)) {
security.checkConnect(hostName, -1);
}
} catch (SecurityException e) {
return ipAddressToString(ipaddress);
}
return hostName;
}
/**
* Gets the fully qualified domain name for the host associated with this IP
* address. If a security manager is set, it is checked if the method caller
* is allowed to get the hostname. Otherwise, the textual representation in
* a dotted-quad-notation is returned.
*
* @return the fully qualified domain name of this IP address.
*/
public String getCanonicalHostName() {
String canonicalName;
try {
int address = 0;
if (ipaddress.length == 4) {
address = bytesToInt(ipaddress, 0);
if (address == 0) {
return ipAddressToString(ipaddress);
}
}
canonicalName = getHostByAddrImpl(ipaddress).hostName;
} catch (UnknownHostException e) {
return ipAddressToString(ipaddress);
}
SecurityManager security = System.getSecurityManager();
try {
// Only check host names, not addresses
if (security != null && isHostName(canonicalName)) {
security.checkConnect(canonicalName, -1);
}
} catch (SecurityException e) {
return ipAddressToString(ipaddress);
}
return canonicalName;
}
/**
* Returns an {@code InetAddress} for the local host if possible, or the
* loopback address otherwise. This method works by getting the hostname,
* performing a DNS lookup, and then taking the first returned address.
* For devices with multiple network interfaces and/or multiple addresses
* per interface, this does not necessarily return the {@code InetAddress}
* you want.
*
* <p>Multiple interface/address configurations were relatively rare
* when this API was designed, but multiple interfaces are the default for
* modern mobile devices (with separate wifi and radio interfaces), and
* the need to support both IPv4 and IPv6 has made multiple addresses
* commonplace. New code should thus avoid this method except where it‘s
* basically being used to get a loopback address or equivalent.
*
* <p>There are two main ways to get a more specific answer:
* <ul>
* <li>If you have a connected socket, you should probably use
* {@link Socket#getLocalAddress} instead: that will give you the address
* that‘s actually in use for that connection. (It‘s not possible to ask
* the question "what local address would a connection to a given remote
* address use?"; you have to actually make the connection and see.)</li>
* <li>For other use cases, see {@link NetworkInterface}, which lets you
* enumerate all available network interfaces and their addresses.</li>
* </ul>
*
* <p>Note that if the host doesn‘t have a hostname set – as
* Android devices typically don‘t – this method will
* effectively return the loopback address, albeit by getting the name
* {@code localhost} and then doing a lookup to translate that to
* {@code 127.0.0.1}.
*
* @return an {@code InetAddress} representing the local host, or the
* loopback address.
* @throws UnknownHostException
* if the address lookup fails.
*/
public static InetAddress getLocalHost() throws UnknownHostException {
String host = gethostname();
SecurityManager security = System.getSecurityManager();
try {
if (security != null) {
security.checkConnect(host, -1);
}
} catch (SecurityException e) {
return Inet4Address.LOOPBACK;
}
return lookupHostByName(host)[0];
}
private static native String gethostname();
/**
* Gets the hashcode of the represented IP address.
*
* @return the appropriate hashcode value.
*/
@Override
public int hashCode() {
// BEGIN android-changed
return Arrays.hashCode(ipaddress);
// END android-changed
}
// BEGIN android-changed
/*
* Returns whether this address is an IP multicast address or not. This
* implementation returns always {@code false}.
*
* @return {@code true} if this address is in the multicast group, {@code
* false} otherwise.
*/
public boolean isMulticastAddress() {
return false;
}
// END android-changed
/**
* Resolves a hostname to its IP addresses using a cache.
*
* @param host the hostname to resolve.
* @return the IP addresses of the host.
*/
// BEGIN android-changed
private static InetAddress[] lookupHostByName(String host) throws UnknownHostException {
// Do we have a result cached?
InetAddress[] cachedResult = addressCache.get(host);
if (cachedResult != null) {
if (cachedResult.length > 0) {
// A cached positive result.
return cachedResult;
} else {
// A cached negative result.
throw new UnknownHostException(host);
}
}
try {
InetAddress[] addresses = bytesToInetAddresses(getaddrinfo(host), host);
addressCache.put(host, addresses);
return addresses;
} catch (UnknownHostException e) {
addressCache.putUnknownHost(host);
throw new UnknownHostException(host);
}
}
private static native byte[][] getaddrinfo(String name) throws UnknownHostException;
// END android-changed
// BEGIN android-deleted
// static native InetAddress[] getAliasesByNameImpl(String name)
// throws UnknownHostException;
// END android-deleted
/**
* Query the IP stack for the host address. The host is in address form.
*
* @param addr
* the host address to lookup.
* @throws UnknownHostException
* if an error occurs during lookup.
*/
// BEGIN android-changed
// static native InetAddress getHostByAddrImpl(byte[] addr)
// throws UnknownHostException;
static InetAddress getHostByAddrImpl(byte[] addr)
throws UnknownHostException {
if (addr.length == 4) {
return new Inet4Address(addr, getnameinfo(addr));
} else if (addr.length == 16) {
return new Inet6Address(addr, getnameinfo(addr));
} else {
throw new UnknownHostException(Msg.getString(
"K0339")); //$NON-NLS-1$
}
}
/**
* Resolves an IP address to a hostname. Thread safe.
*/
private static native String getnameinfo(byte[] addr);
// END android-changed
// BEGIN android-removed
// static int inetAddr(String host) throws UnknownHostException
// END android-removed
// BEGIN android-removed
// static native int inetAddrImpl(String host) throws UnknownHostException;
// END android-removed
// BEGIN android-removed
// static native String inetNtoaImpl(int hipAddr);
// END android-removed
// BEGIN android-removed
// static native InetAddress getHostByNameImpl(String name) throws UnknownHostException;
// END android-removed
static String getHostNameInternal(String host, boolean isCheck) throws UnknownHostException {
if (host == null || 0 == host.length()) {
return Inet4Address.LOOPBACK.getHostAddress();
}
if (isHostName(host)) {
if (isCheck) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkConnect(host, -1);
}
}
return lookupHostByName(host)[0].getHostAddress();
}
return host;
}
/**
* Returns a string containing a concise, human-readable description of this
* IP address.
*
* @return the description, as host/address.
*/
@Override
public String toString() {
return (hostName == null ? "" : hostName) + "/" + getHostAddress(); //$NON-NLS-1$ //$NON-NLS-2$
}
/**
* Returns true if the string is a host name, false if it is an IP Address.
*/
private static boolean isHostName(String value) {
try {
NETIMPL.ipStringToByteArray(value);
return false;
} catch (UnknownHostException e) {
return true;
}
}
/**
* Returns whether this address is a loopback address or not. This
* implementation returns always {@code false}. Valid IPv4 loopback
* addresses are 127.d.d.d The only valid IPv6 loopback address is ::1.
*
* @return {@code true} if this instance represents a loopback address,
* {@code false} otherwise.
*/
public boolean isLoopbackAddress() {
return false;
}
/**
* Returns whether this address is a link-local address or not. This
* implementation returns always {@code false}.
* <p>
* Valid IPv6 link-local addresses are FE80::0 through to
* FEBF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF.
* <p>
* There are no valid IPv4 link-local addresses.
*
* @return {@code true} if this instance represents a link-local address,
* {@code false} otherwise.
*/
public boolean isLinkLocalAddress() {
return false;
}
/**
* Returns whether this address is a site-local address or not. This
* implementation returns always {@code false}.
* <p>
* Valid IPv6 site-local addresses are FEC0::0 through to
* FEFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF.
* <p>
* There are no valid IPv4 site-local addresses.
*
* @return {@code true} if this instance represents a site-local address,
* {@code false} otherwise.
*/
public boolean isSiteLocalAddress() {
return false;
}
/**
* Returns whether this address is a global multicast address or not. This
* implementation returns always {@code false}.
* <p>
* Valid IPv6 link-global multicast addresses are FFxE:/112 where x is a set
* of flags, and the additional 112 bits make up the global multicast
* address space.
* <p>
* Valid IPv4 global multicast addresses are between: 224.0.1.0 to
* 238.255.255.255.
*
* @return {@code true} if this instance represents a global multicast
* address, {@code false} otherwise.
*/
public boolean isMCGlobal() {
return false;
}
/**
* Returns whether this address is a node-local multicast address or not.
* This implementation returns always {@code false}.
* <p>
* Valid IPv6 node-local multicast addresses are FFx1:/112 where x is a set
* of flags, and the additional 112 bits make up the node-local multicast
* address space.
* <p>
* There are no valid IPv4 node-local multicast addresses.
*
* @return {@code true} if this instance represents a node-local multicast
* address, {@code false} otherwise.
*/
public boolean isMCNodeLocal() {
return false;
}
/**
* Returns whether this address is a link-local multicast address or not.
* This implementation returns always {@code false}.
* <p>
* Valid IPv6 link-local multicast addresses are FFx2:/112 where x is a set
* of flags, and the additional 112 bits make up the link-local multicast
* address space.
* <p>
* Valid IPv4 link-local addresses are between: 224.0.0.0 to 224.0.0.255
*
* @return {@code true} if this instance represents a link-local multicast
* address, {@code false} otherwise.
*/
public boolean isMCLinkLocal() {
return false;
}
/**
* Returns whether this address is a site-local multicast address or not.
* This implementation returns always {@code false}.
* <p>
* Valid IPv6 site-local multicast addresses are FFx5:/112 where x is a set
* of flags, and the additional 112 bits make up the site-local multicast
* address space.
* <p>
* Valid IPv4 site-local addresses are between: 239.252.0.0 to
* 239.255.255.255
*
* @return {@code true} if this instance represents a site-local multicast
* address, {@code false} otherwise.
*/
public boolean isMCSiteLocal() {
return false;
}
/**
* Returns whether this address is a organization-local multicast address or
* not. This implementation returns always {@code false}.
* <p>
* Valid IPv6 organization-local multicast addresses are FFx8:/112 where x
* is a set of flags, and the additional 112 bits make up the
* organization-local multicast address space.
* <p>
* Valid IPv4 organization-local addresses are between: 239.192.0.0 to
* 239.251.255.255
*
* @return {@code true} if this instance represents a organization-local
* multicast address, {@code false} otherwise.
*/
public boolean isMCOrgLocal() {
return false;
}
/**
* Returns whether this is a wildcard address or not. This implementation
* returns always {@code false}.
*
* @return {@code true} if this instance represents a wildcard address,
* {@code false} otherwise.
*/
public boolean isAnyLocalAddress() {
return false;
}
/**
* Tries to reach this {@code InetAddress}. This method first tries to use
* ICMP <i>(ICMP ECHO REQUEST)</i>. When first step fails, a TCP connection
* on port 7 (Echo) of the remote host is established.
*
* @param timeout
* timeout in milliseconds before the test fails if no connection
* could be established.
* @return {@code true} if this address is reachable, {@code false}
* otherwise.
* @throws IOException
* if an error occurs during an I/O operation.
* @throws IllegalArgumentException
* if timeout is less than zero.
*/
public boolean isReachable(int timeout) throws IOException {
return isReachable(null, 0, timeout);
}
/**
* Tries to reach this {@code InetAddress}. This method first tries to use
* ICMP <i>(ICMP ECHO REQUEST)</i>. When first step fails, a TCP connection
* on port 7 (Echo) of the remote host is established.
*
* @param netif
* the network interface on which to connection should be
* established.
* @param ttl
* the maximum count of hops (time-to-live).
* @param timeout
* timeout in milliseconds before the test fails if no connection
* could be established.
* @return {@code true} if this address is reachable, {@code false}
* otherwise.
* @throws IOException
* if an error occurs during an I/O operation.
* @throws IllegalArgumentException
* if ttl or timeout is less than zero.
*/
public boolean isReachable(NetworkInterface netif, final int ttl,
final int timeout) throws IOException {
if (0 > ttl || 0 > timeout) {
throw new IllegalArgumentException(Msg.getString("K0051")); //$NON-NLS-1$
}
boolean reachable = false;
if (null == netif) {
// network interface is null, binds to no address
// BEGIN android-changed
// reachable = NETIMPL.isReachableByICMP(this, null, ttl, timeout);
// if (!reachable) {
reachable = isReachableByTCP(this, null, timeout);
// }
// END android-changed
} else {
// Not Bind to any address
if (null == netif.addresses) {
return false;
}
// binds to all address on this NetworkInterface, tries ICMP ping
// first
// BEGIN android-changed
// reachable = isReachableByICMPUseMultiThread(netif, ttl, timeout);
// if (!reachable) {
// tries TCP echo if ICMP ping fails
reachable = isReachableByMultiThread(netif, ttl, timeout);
// }
// END adnroid-changed
}
return reachable;
}
/*
* Uses multi-Thread to try if isReachable, returns true if any of threads
* returns in time
*/
// BEGIN android-changed
private boolean isReachableByMultiThread(NetworkInterface netif,
final int ttl, final int timeout)
// END android-changed
throws IOException {
if (null == netif.addresses) {
return false;
}
Enumeration<InetAddress> addresses = netif.getInetAddresses();
reached = false;
addrCount = netif.addresses.length;
boolean needWait = false;
while (addresses.hasMoreElements()) {
final InetAddress addr = addresses.nextElement();
// loopback interface can only reach to local addresses
if (addr.isLoopbackAddress()) {
Enumeration<NetworkInterface> NetworkInterfaces = NetworkInterface
.getNetworkInterfaces();
while (NetworkInterfaces.hasMoreElements()) {
NetworkInterface networkInterface = NetworkInterfaces
.nextElement();
Enumeration<InetAddress> localAddresses = networkInterface
.getInetAddresses();
while (localAddresses.hasMoreElements()) {
if (InetAddress.this.equals(localAddresses
.nextElement())) {
return true;
}
}
}
synchronized (waitReachable) {
addrCount--;
if (addrCount == 0) {
// if count equals zero, all thread
// expired,notifies main thread
waitReachable.notifyAll();
}
}
continue;
}
needWait = true;
new Thread() {
@Override
public void run() {
boolean threadReached = false;
// BEGIN android-changed
// if isICMP, tries ICMP ping, else TCP echo
// if (isICMP) {
// threadReached = NETIMPL.isReachableByICMP(
// InetAddress.this, addr, ttl, timeout);
// } else {
try {
threadReached = isReachableByTCP(addr,
InetAddress.this, timeout);
} catch (IOException e) {
// do nothing
}
// }
// END android-changed
synchronized (waitReachable) {
if (threadReached) {
// if thread reached this address, sets reached to
// true and notifies main thread
reached = true;
waitReachable.notifyAll();
} else {
addrCount--;
if (0 == addrCount) {
// if count equals zero, all thread
// expired,notifies main thread
waitReachable.notifyAll();
}
}
}
}
}.start();
}
if (needWait) {
synchronized (waitReachable) {
try {
while (!reached && (addrCount != 0)) {
// wait for notification
waitReachable.wait(1000);
}
} catch (InterruptedException e) {
// do nothing
}
return reached;
}
}
return false;
}
// BEGIN android-removed
// private boolean isReachableByICMPUseMultiThread(NetworkInterface netif,
// int ttl, int timeout) throws IOException {
// return isReachableByMultiThread(netif, ttl, timeout, true);
// }
//
// private boolean isReachableByTCPUseMultiThread(NetworkInterface netif,
// int ttl, int timeout) throws IOException {
// return isReachableByMultiThread(netif, ttl, timeout, false);
// }
// END android-removed
private boolean isReachableByTCP(InetAddress dest, InetAddress source,
int timeout) throws IOException {
FileDescriptor fd = new FileDescriptor();
// define traffic only for parameter
int traffic = 0;
boolean reached = false;
NETIMPL.createStreamSocket(fd, NetUtil.preferIPv4Stack());
try {
if (null != source) {
NETIMPL.bind(fd, source, 0);
}
NETIMPL.connectStreamWithTimeoutSocket(fd, 7, timeout, traffic,
dest);
reached = true;
} catch (IOException e) {
if (ERRMSG_CONNECTION_REFUSED.equals(e.getMessage())) {
// Connection refused means the IP is reachable
reached = true;
}
}
NETIMPL.socketClose(fd);
return reached;
}
/**
* Returns the {@code InetAddress} corresponding to the array of bytes. In
* the case of an IPv4 address there must be exactly 4 bytes and for IPv6
* exactly 16 bytes. If not, an {@code UnknownHostException} is thrown.
* <p>
* The IP address is not validated by a name service.
* <p>
* The high order byte is {@code ipAddress[0]}.
*
* @param ipAddress
* is either a 4 (IPv4) or 16 (IPv6) byte long array.
* @return an {@code InetAddress} instance representing the given IP address
* {@code ipAddress}.
* @throws UnknownHostException
* if the given byte array has no valid length.
*/
public static InetAddress getByAddress(byte[] ipAddress)
throws UnknownHostException {
// simply call the method by the same name specifying the default scope
// id of 0
return getByAddressInternal(null, ipAddress, 0);
}
/**
* Returns the {@code InetAddress} corresponding to the array of bytes. In
* the case of an IPv4 address there must be exactly 4 bytes and for IPv6
* exactly 16 bytes. If not, an {@code UnknownHostException} is thrown. The
* IP address is not validated by a name service. The high order byte is
* {@code ipAddress[0]}.
*
* @param ipAddress
* either a 4 (IPv4) or 16 (IPv6) byte array.
* @param scope_id
* the scope id for an IPV6 scoped address. If not a scoped
* address just pass in 0.
* @return the InetAddress
* @throws UnknownHostException
*/
static InetAddress getByAddress(byte[] ipAddress, int scope_id)
throws UnknownHostException {
return getByAddressInternal(null, ipAddress, scope_id);
}
private static boolean isIPv4MappedAddress(byte ipAddress[]) {
// Check if the address matches ::FFFF:d.d.d.d
// The first 10 bytes are 0. The next to are -1 (FF).
// The last 4 bytes are varied.
if (ipAddress == null || ipAddress.length != 16) {
return false;
}
for (int i = 0; i < 10; i++) {
if (ipAddress[i] != 0) {
return false;
}
}
if (ipAddress[10] != -1 || ipAddress[11] != -1) {
return false;
}
return true;
}
private static byte[] ipv4MappedToIPv4(byte[] mappedAddress) {
byte[] ipv4Address = new byte[4];
for(int i = 0; i < 4; i++) {
ipv4Address[i] = mappedAddress[12 + i];
}
return ipv4Address;
}
/**
* Returns the {@code InetAddress} corresponding to the array of bytes, and
* the given hostname. In the case of an IPv4 address there must be exactly
* 4 bytes and for IPv6 exactly 16 bytes. If not, an {@code
* UnknownHostException} will be thrown.
* <p>
* The host name and IP address are not validated.
* <p>
* The hostname either be a machine alias or a valid IPv6 or IPv4 address
* format.
* <p>
* The high order byte is {@code ipAddress[0]}.
*
* @param hostName
* the string representation of hostname or IP address.
* @param ipAddress
* either a 4 (IPv4) or 16 (IPv6) byte long array.
* @return an {@code InetAddress} instance representing the given IP address
* and hostname.
* @throws UnknownHostException
* if the given byte array has no valid length.
*/
public static InetAddress getByAddress(String hostName, byte[] ipAddress)
throws UnknownHostException {
// just call the method by the same name passing in a default scope id
// of 0
return getByAddressInternal(hostName, ipAddress, 0);
}
/**
* Returns the {@code InetAddress} corresponding to the array of bytes, and
* the given hostname. In the case of an IPv4 address there must be exactly
* 4 bytes and for IPv6 exactly 16 bytes. If not, an {@code
* UnknownHostException} is thrown. The host name and IP address are not
* validated. The hostname either be a machine alias or a valid IPv6 or IPv4
* address format. The high order byte is {@code ipAddress[0]}.
*
* @param hostName
* string representation of hostname or IP address.
* @param ipAddress
* either a 4 (IPv4) or 16 (IPv6) byte array.
* @param scope_id
* the scope id for a scoped address. If not a scoped address
* just pass in 0.
* @return the InetAddress
* @throws UnknownHostException
*/
static InetAddress getByAddressInternal(String hostName, byte[] ipAddress,
int scope_id) throws UnknownHostException {
if (ipAddress == null) {
// We don‘t throw NullPointerException here for RI compatibility,
// but we do say "address is null" (K0331), instead of "addr is of
// illegal length".
throw new UnknownHostException(
Msg.getString("K0331", hostName)); //$NON-NLS-1$
}
switch (ipAddress.length) {
case 4:
return new Inet4Address(ipAddress.clone());
case 16:
// First check to see if the address is an IPv6-mapped
// IPv4 address. If it is, then we can make it a IPv4
// address, otherwise, we‘ll create an IPv6 address.
if (isIPv4MappedAddress(ipAddress)) {
return new Inet4Address(ipv4MappedToIPv4(ipAddress));
} else {
return new Inet6Address(ipAddress.clone(), scope_id);
}
default:
if (hostName != null) {
// "Invalid IP Address is neither 4 or 16 bytes: <hostName>"
throw new UnknownHostException(
Msg.getString("K0332", hostName)); //$NON-NLS-1$
} else {
// "Invalid IP Address is neither 4 or 16 bytes"
throw new UnknownHostException(
Msg.getString("K0339")); //$NON-NLS-1$
}
}
}
/**
* Takes the integer and chops it into 4 bytes, putting it into the byte
* array starting with the high order byte at the index start. This method
* makes no checks on the validity of the parameters.
*/
static void intToBytes(int value, byte bytes[], int start) {
// Shift the int so the current byte is right-most
// Use a byte mask of 255 to single out the last byte.
bytes[start] = (byte) ((value >> 24) & 255);
bytes[start + 1] = (byte) ((value >> 16) & 255);
bytes[start + 2] = (byte) ((value >> 8) & 255);
bytes[start + 3] = (byte) (value & 255);
}
/**
* Takes the byte array and creates an integer out of four bytes starting at
* start as the high-order byte. This method makes no checks on the validity
* of the parameters.
*/
static int bytesToInt(byte bytes[], int start) {
// First mask the byte with 255, as when a negative
// signed byte converts to an integer, it has bits
// on in the first 3 bytes, we are only concerned
// about the right-most 8 bits.
// Then shift the rightmost byte to align with its
// position in the integer.
int value = ((bytes[start + 3] & 255))
| ((bytes[start + 2] & 255) << 8)
| ((bytes[start + 1] & 255) << 16)
| ((bytes[start] & 255) << 24);
return value;
}
private static final ObjectStreamField[] serialPersistentFields = {
new ObjectStreamField("address", Integer.TYPE), //$NON-NLS-1$
new ObjectStreamField("family", Integer.TYPE), //$NON-NLS-1$
new ObjectStreamField("hostName", String.class) }; //$NON-NLS-1$
private void writeObject(ObjectOutputStream stream) throws IOException {
ObjectOutputStream.PutField fields = stream.putFields();
if (ipaddress == null) {
fields.put("address", 0); //$NON-NLS-1$
} else {
fields.put("address", bytesToInt(ipaddress, 0)); //$NON-NLS-1$
}
fields.put("family", family); //$NON-NLS-1$
fields.put("hostName", hostName); //$NON-NLS-1$
stream.writeFields();
}
private void readObject(ObjectInputStream stream) throws IOException,
ClassNotFoundException {
ObjectInputStream.GetField fields = stream.readFields();
int addr = fields.get("address", 0); //$NON-NLS-1$
ipaddress = new byte[4];
intToBytes(addr, ipaddress, 0);
hostName = (String) fields.get("hostName", null); //$NON-NLS-1$
family = fields.get("family", 2); //$NON-NLS-1$
}
/*
* The spec requires that if we encounter a generic InetAddress in
* serialized form then we should interpret it as an Inet4 address.
*/
private Object readResolve() throws ObjectStreamException {
return new Inet4Address(ipaddress, hostName);
}
}
下面是已经登录设备线程中监听用户上线操作，再监听完成后并发送一个回执：（当然其中也包括了收到应答之后的操作）
@Override
public void run() {
// TODO Auto-generated method stub
while(onWork){
try {
udpSocket.receive(udpResPacket);
} catch (IOException e) {
// TODO Auto-generated catch block
onWork = false;
if(udpResPacket != null){
udpResPacket = null;
}
if(udpSocket != null){
udpSocket.close();
udpSocket = null;
}
udpThread = null;
Log.e(TAG, "UDP数据包接收失败！线程停止");
break;
}
if(udpResPacket.getLength() == 0){
Log.i(TAG, "无法接收UDP数据或者接收到的UDP数据为空");
continue;
}
String ipmsgStr = "";
try {
ipmsgStr = new String(resBuffer, 0, udpResPacket.getLength(),"gbk");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e(TAG, "接收数据时，系统不支持GBK编码");
}//截取收到的数据
Log.i(TAG, "接收到的UDP数据内容为:" + ipmsgStr);
IpMessageProtocol ipmsgPro = new IpMessageProtocol(ipmsgStr); //
int commandNo = ipmsgPro.getCommandNo();
int commandNo2 = 0x000000FF & commandNo; //获取命令字
switch(commandNo2){
case IpMessageConst.IPMSG_BR_ENTRY: { //收到上线数据包，添加用户，并回送IPMSG_ANSENTRY应答。
addUser(ipmsgPro); //添加用户
MyFeiGeBaseActivity.sendEmptyMessage(IpMessageConst.IPMSG_BR_ENTRY);
//下面构造回送报文内容
IpMessageProtocol ipmsgSend = new IpMessageProtocol();
ipmsgSend.setVersion(String.valueOf(IpMessageConst.VERSION));
ipmsgSend.setSenderName(selfName);
ipmsgSend.setSenderHost(selfGroup);
ipmsgSend.setCommandNo(IpMessageConst.IPMSG_ANSENTRY); //回送报文命令
ipmsgSend.setAdditionalSection(selfName + "\0" ); //附加信息里加入用户名和分组信息
sendUdpData(ipmsgSend.getProtocolString(), udpResPacket.getAddress(), udpResPacket.getPort()); //发送数据
}
break;
case IpMessageConst.IPMSG_ANSENTRY: { //收到上线应答，更新在线用户列表
addUser(ipmsgPro);
MyFeiGeBaseActivity.sendEmptyMessage(IpMessageConst.IPMSG_ANSENTRY);
}
break;
} //end of switch
if(udpResPacket != null){ //每次接收完UDP数据后，重置长度。否则可能会导致下次收到数据包被截断。
udpResPacket.setLength(BUFFERLENGTH);
}
}
udpThread = null;
}
更新列表动作到这里就基本结束了，下线的理论是差不多的，我们在退出应用的时候去发送一个广播过程和登录是一样的，这里就不再花篇幅去罗嗦了。
最后把效果给大家看一下吧，UI不得不承认是很丑的：