msgcodes.txt

sig   = signature(dest)
delta = delta(src, sig)
patch(dest, delta)

message format:
# is a delimeter
[messagecode][#][clientid][#][filename][#][data]

SERVERID : 'S0000'

Client DATABASE <fileid, server_m_time, client_m_time>
Server DATABASE <fileid, server_m_time, client_m_time>

timestamp = (server_m_time, client_m_time)

CREQ    :   0001   : data : timestamp   , both times are separated by #
SENDSIG :   0002   : data : signature
SENDDEL :   0003   : data : delta
REQSIG  :   0004   : data : \0
REQSMT  :   0005   : data : \0
SENDSMT :   0006   : data : server.server_m_time
SENDNOC :   0007   : data : \0
REQTOT :    0008   : data : \0
SENDDATA:   0009   : data : filedata
SERVSYNC:   0010   : data : \0
CONFLICT:   0011   : data : \0



Sync-ing Algorithm
-------------------------------------------------------------------------------------------------------------------
for each file
C : update client.client_m_time from stat

C : client sends CREQ packet to server

S : if not present request to send the total file
        client sends the total file to server
    else
    if server.server_m_time == client.server_m_time // sent by client, client is synced with server but has new upates, need to be synced
        if server.client_m_time == client.client_m_time                 (1)
            NO CHANGE                                               SENDNOC
        else:                                                           (2)
            if client.client_m_time > server.client_m_time  // obviously
                request client to give updates
                [dest = server, src = client]
                1. send a signature to client       (server)        SENDSIG
                2. compute delta and send to server (client)        SENDDEL
                3. patch to the dest file           (server)
                   update server.client_m_time 
                   update server.server_m_time
            else    // only when parallel multiple access
                CONFLICT
            
    else:   // server.server_m_time != client.server_m_time            // client is not synced with server (for a specific client)

            // implies some other client has updated this data in server
            // obviously (server.server_m_time > client.server_m_time)
            
            if client.client_m_time > server.client_m_time  // present client has recent data
                [dest = server, src = client]
                1. send a signature to client       (server)        SENDSIG
                2. compute delta and send to server (client)        SENDDEL
                3. patch to the dest file           (server)
                   update server.server_m_time = getmtime(file)
                4. send server.server_m_time to client(server)      SENDSMT
                5. update client.server_m_time      (client)
            else                                            // present client has old data
                [dest = client, src = server]
                1. REQ client to send a signature  (server)         REQSIG
                2. send a signature to server      (client)         SENDSIG
                3. compute delta and send to client(server)         SENDDEL
                4. patch to the dest file          (client)
                   update client.client_m_time     
                5. request server to send server.server_m_time      REQSMT
                6. send server.server_m_time       (server)         SENDSMT
                7. update client.server_m_time     (client)