cSMTP

Overview

cSMTP is a simple SMTP (Simple Mail Transfer Protocol) client written in C. It demonstrates the basics of connecting to an SMTP server, sending email commands, and transmitting an email message from a source to a destination address.

Features

• Establishes a connection to an SMTP server
• Sends HELO, MAIL FROM, RCPT TO, and DATA commands
• Reads server responses
• Handles simple email sending with specified source and destination addresses

Files

• Csmtp.c: The main program file containing the implementation of the SMTP client.
• Csmtp.h: The header file containing function prototypes and necessary includes.

Prerequisites

To compile and run the cSMTP client, you need:

• A C compiler (e.g., gcc)
• A Unix-like operating system (Linux, macOS, etc.)
• Network access to an SMTP server

Installation

1. Clone the repository:

   git clone https://github.com/yourusername/cSMTP.git

2. Navigate to the repository directory:

   cd cSMTP

3. Compile the code:

   gcc -o cSMTP Csmtp.c

Usage

To run the cSMTP client, use the following command:

./cSMTP <file_with_addresses> <smtp_server> [port_number]

• <file_with_addresses>: A file containing the source and destination email addresses. The source address should be on the first line, and the destination address on the second line.
• <smtp_server>: The hostname or IP address of the SMTP server.
• [port_number] (optional): The port number of the SMTP server (default is 25).

Example

./cSMTP addresses.txt smtp.example.com 587

In this example, addresses.txt contains:

source@example.com
destination@example.com

Code Explanation

Csmtp.c

The main implementation file for the cSMTP client. It includes:

• Establishing a connection to the SMTP server
• Sending SMTP commands and handling server responses
• Reading email addresses from a file
• Sending email content from the file

Csmtp.h

The header file defining function prototypes and necessary includes for the SMTP client.

Functions

Csmtp.c

• int main(int argc, char **argv): The main function to execute the SMTP client.
• int getLine(int fd, char* line, int lim): Reads a line of data from the socket.
• void readServer(int fd, char *line, int *lim, char *postfix): Reads the server response.
• int checkReply(char reply): Checks the server reply code.
• char* getPostfix(char* header, char* postfix): Extracts postfix from the server reply header.

Csmtp.h

• char* getPostfix(char *header, char *postfix): Function prototype for extracting postfix from server reply header.
• void readServer(int fd, char *line, int* lim, char *postfix): Function prototype for reading server response.
• int checkReply(char reply): Function prototype for checking server reply code.
• int getLine(int fd, char line[], int max): Function prototype for getting a line of data from the socket.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Contributing

Contributions are welcome! Please open an issue or submit a pull request for any improvements or bug fixes.

Acknowledgments

This project was created by Uriel Shani as a simple demonstration of an SMTP client in C.

For any questions or issues, please contact the repository owner.