The details of the port numbers for my project as as follows:
// UDP port numbers for connections between server M and server A, B and C
SERVER_A_UDP_PORT 21979
SERVER_B_UDP_PORT 22979
SERVER_C_UDP_PORT 23979
SERVER_M_UDP_PORT 24979 

// Port numbers for TCP connections
CLIENT_A_TCP_PORT 25979 
CLIENT_B_TCP_PORT 26979

The code files I have created for this project are:

1.  serverM.cpp : 
        This is the file created for the Main Server. 

        The main server runs persistently, till the user terminates it.

        The main server listens for and receives command entered by Client A and Client B.

        It then identifies the command and then calls functions as needed to perform the task and communicate with 
        the backend servers A, B and C.

        It receives the transaction logs and length of transaction log (for a particular user or all logs) from 
        servers A, B and C.

        It returns the status of completion of the client request

        REUSED CODE:
        I have implemented the method - accept_client_sockets() in reference with the following link - https://stackoverflow.com/questions/15560336/listen-to-multiple-ports-from-one-server
        I have modified the code for reading lines from a file from the following link - https://www.geeksforgeeks.org/stringstream-c-applications/
        I have modified the code for sorting the vector that stores the logs received from the following link - https://www.geeksforgeeks.org/sorting-a-vector-in-c/


2.  serverA.cpp : 
        This is the file for the backend server A.

        The server A runs persistently, till the user terminates it.

        On bootup, the server reads the file "block1.txt" and creates 3 global unordered maps coinsFrom, coinsTo and coinCount to store details regarding the existing transactions.

        The backend server receives the command from the Main Server.

        It then proceeds to either check if the user(s) exist or to return the logs for either a particular user 
        or for all users.

        And returns logs if a user(s) exists or in case of all logs request, returns all logs.

        In case of a request to add a transaction to the log file, it adds it to "block1.txt".

        REUSED CODE:
        I have modified the code from this site to split char* array by delimeter and save data into unordered maps - https://www.cplusplus.com/forum/beginner/56543/
        I have modified the code from this site to create the pairs to add into the global maps - https://www.tutorialspoint.com/cpp_standard_library/cpp_utility_make_pair.htm


2.  serverB.cpp : 
        This is the file for the backend server B.

        The server B runs persistently, till the user terminates it.

        On bootup, the server reads the file "block2.txt" and creates 3 global unordered maps coinsFrom, coinsTo and coinCount to store details regarding the existing transactions.

        The backend server receives the command from the Main Server.

        It then proceeds to either check if the user(s) exist or to return the logs for either a particular user 
        or for all users.

        And returns logs if a user(s) exists or in case of all logs request, returns all logs.

        In case of a request to add a transaction to the log file, it adds it to "block2.txt".

        REUSED CODE:
        I have modified the code from this site to split char* array by delimeter and save data into unordered maps - https://www.cplusplus.com/forum/beginner/56543/
        I have modified the code from this site to create the pairs to add into the global maps - https://www.tutorialspoint.com/cpp_standard_library/cpp_utility_make_pair.htm

2.  serverC.cpp : 
        This is the file for the backend server C.

        The server C runs persistently, till the user terminates it.

        On bootup, the server reads the file "block3.txt" and creates 3 global unordered maps coinsFrom, coinsTo and coinCount to store details regarding the existing transactions.

        The backend server receives the command from the Main Server.

        It then proceeds to either check if the user(s) exist or to return the logs for either a particular user 
        or for all users.

        And returns logs if a user(s) exists or in case of all logs request, returns all logs.

        In case of a request to add a transaction to the log file, it adds it to "block3.txt".

        REUSED CODE:
        I have modified the code from this site to split char* array by delimeter and save data into unordered maps - https://www.cplusplus.com/forum/beginner/56543/
        I have modified the code from this site to create the pairs to add into the global maps - https://www.tutorialspoint.com/cpp_standard_library/cpp_utility_make_pair.htm


5.  clientA.cpp : 
        This is the file for the client A.

        The client does not run persistently.

        It can perform 3 operations: check current balance for user, log a transaction or request that an ordered file with all transactions be created.

        It communicates with server M over TCP and receives status of transaction or current balance of the user and displays it on the terminal.


6.  clientB.cpp : 
        This is the file for the client B.

        The client does not run persistently.

        It can perform 3 operations: check current balance for user, log a transaction or request that an ordered file with all transactions be created.

        It communicates with server M over TCP and receives status of transaction or current balance of the user and displays it on the terminal.


7.  Makefile : It is used to compile all the above files and create the executables. 
    
    The following operations can be performed on the terminal to compile files because of the makefile
    make all, make serverC, make serverT, make serverS, make serverP, make clientA and make clientB.
    
    The servers can then be booted up using the command ./server# where # is either A, B, C, or M. (All servers must be running for the program to work)
    The clients can make requests by using the command ./client# where # is either A or B. (Any one client is enough to make the program run)

Project Idiosyncrasy: The log files "block1.txt", "block2.txt" and "block3.txt" must not have an empty line at the end for the backend servers to run properly.