C and JAVA versions of the example programs for the RCOMP (REDES DE COMPUTADORES) course

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DISCLAIMER:  these code samples are intended for learning purposes, they were planned
for easy reading in the communication protocols perspective. They are not expected
to be efficient or good samples of well-structured software. Error handling is
frequently ignored for the sake of easing the code analysis within the purposed 
objectives.
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Used application protocols are implementation independent, therefore different
implementations like C and Java can communicate with each other without any problem.

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		*** UDP client and server ***

C/udp-cli-srv/udp_srv.c

JAVA/udp-cli-srv/UdpSrv.java
				Supports both IPv4 and IPv6
				(1) Receives a UDP datagram and stores its content in a string.
				Reverse the string.
				Sends the reversed string inside a UDP datagram to the
				originator address/port.
				Repeat (1)

C/udp-cli-srv/udp_cli.c

JAVA/udp-cli-srv/UdpCli.java

				Get the server address as first argument in the command line.
				Server address can be either a DNS hostname, an IPv4 address
				or an IPv6 address.
				(1) Reads a string from keyboard, exits if the string is "exit",
				otherwise sends the string inside a UDP datagram.
				Receives a UDP datagram and prints it contents as a string.
				Repeat (1).



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		*** Reception timeout and UDP broadcast ***


C/udp-cli-srv/udp_cli_bcast.c

JAVA/udp-cli-srv/UdpCliBcast.java

				Same as previous client but no arguments because UDP
				first request is sent in broadcast (255.255.255.255).
				Operates only over IPv4 (in IPv6 there's no broadcast address).
				Only the first request is sent to the broadcast address,
				next requests are sent to the unicast address of the
				server that replies to the first request.

C/udp-cli-srv/udp_cli_to.c

JAVA/udp-cli-srv/UdpCliTo.java

				Same as the first UDP client but with timeout, if there's
				no reply from the server it does not hang forever as
				previous clients.


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		*** TCP client and server ***

C/tcp-cli-srv/tcp_srv_soma.c

JAVA/tcp-cli-srv/TcpSrvSoma.java

				Accepts TCP connections, either over IPv4 or IPv6,
				on each connection receives unsigned integer numbers
				in the form of 4 bytes, LSB (Least Significant Byte)
				first, until integer number zero is received.
				When zero is received, reply to client with the sum
				result in the same format (4 bytes, LSB first).
				If first number received is zero (empty list) closes
				the connection with the client.


JAVA/tcp-cli-srv/TcpCliSoma.java

C/tcp-cli-srv/tcp_cli_soma.c

				Get the server address as first argument in the command line.
				Server address can be either a DNS hostname, an IPv4 address
				or an IPv6 address.
				Establish a TCP connection to the server, read unsigned integers
				from keyboard and send then to the server in the format specified
				above (4 bytes, LSB first).
				When the number is zero read the result from the server.
				If the first number entered is zero, send it to the server and exit.


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		*** Asynchronous reception, a TCP CHAT client, and server ***

C/udp-cli-srv/udp_srv_mport.c

JAVA/udp-cli-srv/UdpSrvMport.java

				UDP server compatible with previous UDP clients that
				is able to receive requests in a set of alternative
				port numbers. The C version makes use of the select()
				function while the Java version uses multiple threads.


C/tcp-chat/tcp_chat_srv.c

JAVA/tcp-chat/TcpChatSrv.java
				Accepts TCP connections, on all active connections
				receives strings as follows: 1st a byte with the
				number of characters in the string and then the
				string itself.
				For each string received retransmits it to every
				active connection, using the form specified above.
				If the string received is empty sends it back to
				than client and closes that client's connection.

C/tcp-chat/tcp_chat_cli.c

JAVA/tcp-chat/TcpChatCli.java

				Get the server address as first argument in the command line.
				Server address can be either a DNS hostname, an IPv4 address
				or an IPv6 address.
				Connect to the server and read the nickname from the keyboard.
				If a string is entered by keyboard, send the nickname and
				the string to the server (in the format described above).
				If the string typed at keyboard is "exit", send an empty
				string to the server, wait for an empty string reply and exit.
				Meanwhile, if a string is received from the server (in the form
				described above) prints it on the screen.

JAVA/tcp-chat/TcpChatCliGui.java

				GUI (swing) version of the above client.
				Server address is prompted in a dialog box.



JAVA/tcp-chat/TcpChatSrvSingleThread.java

				Single thread Java version of the TCP CHAT server, based
				on polling over sockets with a low read timeout.




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		*** Demo HTTP servers ***


C/http-server-form-file-upload/http_srv_form_file_upload.c

JAVA/http-server-form-file-upload/HttpServerFormFileUpload.java

				Get the port number to use as first argument in the
				command line.
				Documents directory is sub-folder www/
				Reply to GET requests for some files types:
				(HTML,PDF,GIF,PNG,JavaSript).
				Reply to POST for /upload and /list:
				/upload to upload files with multipart/form-data
				/list to list the folder files




C/http-server-ajax-voting/http_srv_ajax_voting.c

JAVA/http-server-ajax-voting/HttpServerAjaxVoting.java

				Get the port number to use as first argument in the
				command line.
				Documents directory is sub-folder www/
				Reply to GET requests for some files types:
				(HTML,PDF,GIF,PNG,JavaSript).
				Web services: GET /votes and PUT /votes/N (N=1..)

JAVA/http-server-ajax-voting/DemoConsumer.java

				Get the HTTP server's address and port number as
				arguments in the command line.
				Casts 200 votes on the first candidate.





JAVA/http-server-chat/HttpServerChat.java

				Get the port number to use as the first argument in the
				command line.
				Documents directory is sub-folder www/
				Replies to GET requests for some files types in www/:
				(HTML,PDF,GIF,PNG,JavaSript).
				Web services: 	GET /messages/N (N=0..)
						POST /messages
				The server numbers posted messages starting from 0.
				Message 0 is a server's greeting to clients.
				Clients are allowed to get only one message at a
				time, they start by message 0. Only once they get
				a message they should request for the next message.
				When the client requests for a message number not
				yet posted, the server holds the response until the
				message is posted. The client doesn't settle a timeout.
				With this strategy, clients are not required to be
				periodically polling for new messages. 

JAVA/http-server-chat/HttpChatConsumer.java

				Command line consumer/client for HttpServerChat.


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		*** Peer-to-peer CHAT application ***

C/udp-chat/udp_chat.c

JAVA/udp-chat/UdpChat.java

				Gets a nickname from the user (keyboard). 
				Manages a list of active peers. At startup one UDP
				datagram is sent to the broadcast address to announce
				itself, this is the peer-start announcement.
				Also, when a new peer-start announcement is received, a
				peer-start announcement is sent back. Before exiting a
				peer-exit announcement is sent to each active peer.
				Other received UDP datagrams that are not a peer-start
				announcements neither peer-exit announcements are supposed
				to be text messages and are printed at the console.
				When the user enters a text line at the console, it is
				sent to each active peer in active peer list.
				If the typed line is EXIT the peer application exits,
				if it's LIST, then a list of active peers is printed.


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		*** SSL/TLS secure communications ***


C/SSL/check-TLS/check_server_TLS.c
JAVA/SSL/check-TLS/CheckServerTLS.java

				Test the SSL/TLS handshake with a TCP server. The
				first argument it's the server's DNS name. The second
				argument is optional, it's the server's port number,
				the default is 443 (HTTPS).
				This client presents information about the secured
				established connection, e.g. TLS version, cypher suite
				and the server's public key certificate.
				


C/SSL/tcp-cli-srv/tcp_cli_sum_TLS.c
C/SSL/tcp-cli-srv/tcp_srv_sum_TLS.c

				Adaptation of C/tcp-cli-srv to use SSL/TLS. Enforces
				the authentication of both the server and the clients,
				through public key certificates.
				Use "make certs" to create all certificates and private
				keys, this creates files:
					client1.pem client1.key
					client2.pem client2.key
					client3.pem client3.key
					client4.pem client4.key
					server.pem server.key
					authentic-clients.pem
				The last file contains the public key certificates for
				client1, client2, and client3, but not for client4.
				The server demands a client's certificate and it must
				be in "authentic-clients.pem", thus client4 will not be
				authorized.





JAVA/SSL/tcp-cli-srv/TcpCliSumTLS.java
JAVA/SSL/tcp-cli-srv/TcpSrvSumTLS.java

				Adaptation of JAVA/tcp-cli-srv to use SSL/TLS. Enforces
				the authentication of both the server and the clients,
				through public key certificates.
				Use "make certs" to create all certificates and private
				keys, this creates files:
					client1_J.jks client1_J.pem
					client2_J.jks client2_J.pem
					client3_J.jks client3_J.pem
					client4_J.jks client4_J.pem
					server_J.jks  server_J.pem
				Each PEM file contains the entity certificate only.
				Each JKS (Java KeyStore) file contains the entiry certificate
				and private key, together with trusted certificates.
				The server trusts client1_J, client2_J, and client3_J. But
				not client4_J.
				Every client trusts server_J.
					






C/SSL/https-server-ajax-voting/https_srv_ajax_voting.c
JAVA/SSL/https-server-ajax-voting/HttpsServerAjaxVoting.java

				Adaptation of http-server-ajax-voting to use SSL/TLS,
				thus it's a HTTPS server and not a HTTP server.
				Use "make cert" to create the server's public key
				certificate and private key.
				The certificate's CN attribute matches the host where
				"make cert" is run, yet it's a self-signed certificate.
				It will not be trusted by browsers.
				To test, don't forget the typed URL on the browser must
				start by "https://" and not "http://", otherwise the
				browser will not use SSL/TLS and the server will not
				allow it.



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ANDRE MOREIRA
[email protected]
https://www.dei.isep.ipp.pt/~andre
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Departamento de Engenharia Informática (DEI)
https://www.dei.isep.ipp.pt/
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Instituto Superior de Engenharia do Porto (ISEP)
https://www.isep.ipp.pt/
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Instituto Politécnico do Porto (IPP)
https://www.ipp.pt/
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Rua Dr. António Bernardino de Almeida, 431
4249-015 Porto
PORTUGAL
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