├── .gitignore
├── CMakeLists.txt
├── lib
    ├── email.hh
    └── email.cc
├── app
    └── app.cc
├── README.md
└── LICENSE


/.gitignore:
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1 | build/
2 | 


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/CMakeLists.txt:
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 1 | cmake_minimum_required(VERSION 3.20)
 2 | 
 3 | project(email
 4 |     VERSION 1.0
 5 |     LANGUAGES CXX
 6 | )
 7 | 
 8 | set(CMAKE_VERBOSE_MAKEFILE OFF)
 9 | set(CMAKE_CXX_FLAGS "-O3 -Wall -Wextra -pedantic")
10 | 
11 | add_library(email
12 |     STATIC
13 |     lib/email.cc
14 | )
15 | 
16 | add_executable(app
17 |     app/app.cc
18 | )
19 | 
20 | target_include_directories(app
21 |     PUBLIC lib
22 | )
23 | 
24 | target_link_libraries(app
25 |     PRIVATE email
26 | )
27 | 


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/lib/email.hh:
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 1 | #pragma once
 2 | 
 3 | #include <iostream>
 4 | #include <vector>
 5 | 
 6 | class Email {
 7 | 
 8 | 	static Email* instance;
 9 | 
10 | public:
11 | 	static Email* Instance();
12 | 	static void Release();
13 | 	int sendmail(const char *from, std::vector<std::string> recipients, const char *subject, const char *body, const char *hostname, const int port);
14 | 
15 | private:
16 | 	Email();
17 | 	virtual ~Email();
18 | 	void writeSocket(const int sock, const char *str, const char *arg);
19 | };
20 | 


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/app/app.cc:
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 1 | #include <iostream>
 2 | #include <vector>
 3 | #include <email.hh>
 4 | 
 5 | int main() {
 6 | 	Email *email = Email::Instance();
 7 | 	std::vector<std::string> recipients;
 8 | 	recipients.push_back("pepe@mailinator.com");
 9 | 	recipients.push_back("pepa@mailinator.com");
10 | 	
11 | 	int ret = email->sendmail(
12 |         "hola@hotmail.com",                              /* from     */
13 |         recipients,                                      /* to       */
14 |         "Mail subject",                                  /* subject  */
15 |         "Mail body.\n\nCan contain linebreaks.\n\nBye.", /* body     */
16 |         "localhost",                                     /* hostname */
17 |         25                                               /* port     */
18 |     );
19 | 
20 |     if (ret != 0)
21 | 		std::cerr << "Failed to send mail (code: " << ret << ")" << std::endl;
22 |     else
23 | 		std::cout << "Mail successfully sent" << std::endl;
24 | 	
25 | 	email->Release();
26 | 	return ret;
27 | }


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/README.md:
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 1 | # Email #
 2 | 
 3 | Send email in C++ implementing the SMTP protocol.
 4 | 
 5 | ## How to use ##
 6 | 
 7 | ```c++
 8 | Email *email = Email::Instance();
 9 | std::vector<std::string> recipients;
10 | recipients.push_back("recipient1@server.com");
11 | recipients.push_back("recipient2@server.com");
12 | 
13 | int ret = email->sendmail(
14 |     "from@server.com",                               /* from     */
15 |     recipients,                                      /* to       */
16 |     "Mail subject",                                  /* subject  */
17 |     "Mail body.\n\nCan contain linebreaks.\n\nBye.", /* body     */
18 |     "localhost",                                     /* hostname */
19 |     25                                               /* port     */
20 | );
21 | 
22 | if (ret != 0)
23 |     std::cerr << "Failed to send mail (code: " << ret << ")" << std::endl;
24 | else
25 |     std::cout << "Mail successfully sent" << std::endl;
26 | 
27 | email->Release();
28 | ```
29 | 
30 | ## Build
31 | 
32 | To build this project run
33 | 
34 | ```bash
35 | $ mkdir build
36 | $ cd build
37 | $ cmake ..
38 | $ make
39 | ```
40 | 
41 | ## Run
42 | 
43 | To run this project run
44 | 
45 | ```bash
46 | $ ./app
47 | ```
48 | 
49 | ## License
50 | 
51 | [Apache License 2.0](https://choosealicense.com/licenses/apache-2.0/)
52 | 


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/lib/email.cc:
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  1 | #include "email.hh"
  2 | #include <iostream>
  3 | #include <netdb.h>         /* gethostbyname  */
  4 | #include <netinet/in.h>    /* htons          */
  5 | #include <sys/socket.h>
  6 | #include <string.h>
  7 | #include <stdio.h>
  8 | #include <unistd.h>
  9 | 
 10 | using namespace std;
 11 | 
 12 | Email* Email::instance = NULL;
 13 | 
 14 | Email::Email() {}
 15 | 
 16 | Email::~Email() {}
 17 | 
 18 | Email* Email::Instance() {
 19 | 	if(instance == NULL) {
 20 | 		instance = new Email();
 21 | 	}
 22 | 	return instance;
 23 | }
 24 | 
 25 | void Email::Release() {
 26 | 	if(instance) {
 27 | 		delete instance;
 28 | 	}
 29 | 	instance = NULL;
 30 | }
 31 | 
 32 | void Email::writeSocket(const int sock, const char *str, const char *arg) {
 33 | 	char buf[4096];
 34 | 
 35 | 	if(arg != NULL)
 36 | 		snprintf(buf, sizeof(buf), str, arg);
 37 | 	else
 38 | 		snprintf(buf, sizeof(buf), str, NULL);
 39 | 
 40 | 	send(sock, buf, strlen(buf), 0);
 41 | }
 42 | 
 43 | int Email::sendmail(const char *from, std::vector<std::string> recipients, const char *subject, const char *body, const char *hostname, const int port) {
 44 | 	struct hostent *host;
 45 | 	struct sockaddr_in saddr_in;
 46 | 	int sock = 0;
 47 | 	char buf[256];
 48 | 
 49 | 	sock = socket(AF_INET, SOCK_STREAM, 0);
 50 | 	host = gethostbyname(hostname);
 51 | 
 52 | 	saddr_in.sin_family      = AF_INET;
 53 | 	saddr_in.sin_port        = htons((u_short)port);
 54 | 	saddr_in.sin_addr.s_addr = 0;
 55 | 
 56 | 	memcpy((char*) & (saddr_in.sin_addr), host->h_addr, host->h_length);
 57 | 
 58 | 	if(connect(sock, (struct sockaddr*)&saddr_in, sizeof(saddr_in)) == -1) {
 59 | 		return -2;
 60 | 	}
 61 | 
 62 | 	writeSocket(sock, "HELO %s\n",       from);    // greeting
 63 | 	recv(sock, buf, 254, 0);
 64 | 	printf("\nRec: %s", buf);
 65 | 	writeSocket(sock, "MAIL FROM: %s\n", from);    // from
 66 | 	recv(sock, buf, 254, 0);
 67 | 	printf("\nRec: %s", buf);
 68 | 	
 69 | 	for(int i = 0; i < (int)recipients.size(); i++){
 70 | 		writeSocket(sock, "RCPT TO: %s\n",   recipients.at(i).c_str()); // to
 71 | 		//printf("RCPT TO: %s\n", recipients.at(i).c_str());
 72 | 		recv(sock, buf, 254, 0);
 73 | 	}
 74 | 	
 75 | 	printf("\nRec: %s", buf);
 76 | 	writeSocket(sock, "DATA\n",          NULL);    // begin data
 77 | 	recv(sock, buf, 254, 0);
 78 | 	printf("\nRec: %s", buf);
 79 | 
 80 | 	// next comes mail headers
 81 | 	writeSocket(sock, "From: %s\n",      from);
 82 | 	
 83 | 	for(int i = 0; i < (int)recipients.size(); i++){
 84 | 		writeSocket(sock, "To: %s\n",   recipients.at(i).c_str()); // to
 85 | 		//printf("To: %s\n", recipients.at(i).c_str());
 86 | 	}
 87 | 	
 88 | 	writeSocket(sock, "Subject: %s\n",   subject);
 89 | 
 90 | 	writeSocket(sock, "\n",              NULL);
 91 | 
 92 | 	writeSocket(sock, "%s\n",            body);    // data
 93 | 
 94 | 	writeSocket(sock, ".\n",             NULL);    // end data
 95 | 	recv(sock, buf, 254, 0);
 96 | 	printf("\nRec: %s", buf);
 97 | 	writeSocket(sock, "QUIT\n",          NULL);    // terminate
 98 | 
 99 | 	close(sock);
100 | 
101 | 	return 0;
102 | }
103 | 


--------------------------------------------------------------------------------
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