net: Add and document network messages in protocol.h

- Avoids string typos (by making the compiler check)
- Makes it easier to grep for handling/generation of a certain message type
- Refer directly to documentation by following the symbol in IDE
- Move list of valid message types to protocol.cpp:
    protocol.cpp is a more appropriate place for this, and having
    the array there makes it easier to keep things consistent.

src/protocol.cpp

@@ -12,14 +12,68 @@
 # include <arpa/inet.h>
 #endif
 
+namespace NetMsgType {
+const char *VERSION="version";
+const char *VERACK="verack";
+const char *ADDR="addr";
+const char *INV="inv";
+const char *GETDATA="getdata";
+const char *MERKLEBLOCK="merkleblock";
+const char *GETBLOCKS="getblocks";
+const char *GETHEADERS="getheaders";
+const char *TX="tx";
+const char *HEADERS="headers";
+const char *BLOCK="block";
+const char *GETADDR="getaddr";
+const char *MEMPOOL="mempool";
+const char *PING="ping";
+const char *PONG="pong";
+const char *ALERT="alert";
+const char *NOTFOUND="notfound";
+const char *FILTERLOAD="filterload";
+const char *FILTERADD="filteradd";
+const char *FILTERCLEAR="filterclear";
+const char *REJECT="reject";
+const char *SENDHEADERS="sendheaders";
+};
+
 static const char* ppszTypeName[] =
 {
-    "ERROR",
-    "tx",
-    "block",
-    "filtered block"
+    "ERROR", // Should never occur
+    NetMsgType::TX,
+    NetMsgType::BLOCK,
+    "filtered block" // Should never occur
 };
 
+/** All known message types. Keep this in the same order as the list of
+ * messages above and in protocol.h.
+ */
+const static std::string allNetMessageTypes[] = {
+    NetMsgType::VERSION,
+    NetMsgType::VERACK,
+    NetMsgType::ADDR,
+    NetMsgType::INV,
+    NetMsgType::GETDATA,
+    NetMsgType::MERKLEBLOCK,
+    NetMsgType::GETBLOCKS,
+    NetMsgType::GETHEADERS,
+    NetMsgType::TX,
+    NetMsgType::HEADERS,
+    NetMsgType::BLOCK,
+    NetMsgType::GETADDR,
+    NetMsgType::MEMPOOL,
+    NetMsgType::PING,
+    NetMsgType::PONG,
+    NetMsgType::ALERT,
+    NetMsgType::NOTFOUND,
+    NetMsgType::FILTERLOAD,
+    NetMsgType::FILTERADD,
+    NetMsgType::FILTERCLEAR,
+    NetMsgType::REJECT,
+    NetMsgType::SENDHEADERS
+};
+const static std::vector<std::string> allNetMessageTypesVec(allNetMessageTypes, allNetMessageTypes+ARRAYLEN(allNetMessageTypes));
+
 CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn)
 {
     memcpy(pchMessageStart, pchMessageStartIn, MESSAGE_START_SIZE);
@@ -140,3 +194,8 @@ std::string CInv::ToString() const
 {
     return strprintf("%s %s", GetCommand(), hash.ToString());
 }
+
+const std::vector<std::string> &getAllNetMessageTypes()
+{
+    return allNetMessageTypesVec;
+}