EE450_Socket_Project
Name: Ximeng Zhao

What you have done in the assignment.

For this project, I created four programs to utilize socket programming. The purpose
is to process two data file, which contains several countries and the users within the
listed country. Each user has some or no connections with the other users in the country.
Server A and server B will process two set of data files and send the list to the main server.
The client will ask for user input and forward these inputs, the user id and the country
name, to the main server and asking for friend recommendation. A friend is an unconnected
user in the same country who may or may not have some mutual friends. The main server
will send the requested country and user id to the two sub servers. Then, either server A
or server B will find a friend for the requested user in the requested country. The final
recommendation will be forwarded to the client.

What your code files are and what each one of them does. (Please do not repeat the
project description, just name your code files and briefly mention what they do).

Server A/server B: process the data file and send the list of countries to the main server.
Process the requested user id within the requested country and find a friend for the user.
Main server: receive the list of countries from the sub servers. receive the country and user
request from the client. Forward the friend recommendation to the client.
Client: Ask user to input a country name and an user id to forward to the main server for
friend recommendation.

The format of all the messages exchanged.

Server A/B:
"The server A/B is up and running using UDP on port <server
A port number>"
"The server A/B has sent a country list to Main Server"
"The server A/B has received request for finding possible
friends of User<user ID> in <Country Name>"
"User<user ID> does not show up in <Country Name>"
"The server A/B has sent “User<user ID> not found” to Main
Server"
"The server A/B is searching possible friends for User<user
ID> …"
"Here are the results: User<user ID1>, User<user ID2>..."
"The server A/B has sent the result(s) to Main Server"

Main server:
"The Main server is up and running."
"The Main server has received the country list from server
A using UDP over port <Main server UDP port number>"
"The Main server has received the country list from server
B using UDP over port <Main server UDP port number>"
"Server A | Server B
<Country Name 1> | <Country Name 3>
<Country Name 2> |"
"The Main server has received the request on User <user
ID> in <Country Name> from client<client ID> using
TCP over port <Main server TCP port number>"
"<Country Name> does not show up in server A&B"
"The Main Server has sent “Country Name: Not found” to
client1/2 using TCP over port <Main server TCP port
number>"
"<Country Name> shows up in server A/B"
"The Main Server has sent request from User <user ID> to
server A/B using UDP over port <Main server UDP port
number>"
"The Main server has received searching result(s) of User
<user ID> from server<A/B>"
"The Main Server has sent searching result(s) to client
using TCP over port <Main Server TCP port number>"
"The Main server has received “User ID: Not found” from
server <A/B>"
"The Main Server has sent error to client using TCP over
<Main Server UDP port number>"

Client:
"The client is up and running"
"Please enter the User ID:"
"Please enter the Country Name:"
"Client has sent User<user ID> and <Country Name> to
Main Server using TCP"
"<Country Name> not found"
"User<user ID> not found"
"Client has received results from Main Server:"
"User<user ID1>, User<user ID2> is/are possible friend(s)
of User<user ID> in <Country Name>"

Any idiosyncrasy of your project. It should say under what conditions the project
fails, if any.

For client terminal, you have to input a number for user id, and a string for country name.
Otherwise, the code won't be executed correctly.
If there is an exit zombies process, it will show address is already used. You need to kill
the zombie process first and then run.

Reused Code: Did you use code from anywhere for your project? If not, say so. If
so, say what functions and where they're from. (Also identify this with a comment in
the source code.)

TCP and UDP socket initialization, creating, binding, accepting, sending, and receiving
using socket are all from Beej's Tutorial of socket programming.