smtp.c

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>

int main(int argc, char *argv[]) {
        int smtp_fd;
        int seq = 0;
        struct sockaddr_in smtp_s;
        char buf[1024];
        char rec_buf[256];

        if((smtp_fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
                fprintf(stderr, "Error creating socket\n");
                exit(-1);
        }
        memset(&smtp_s, 0, sizeof(smtp_s));
        smtp_s.sin_family = AF_INET;
        smtp_s.sin_addr.s_addr = inet_addr(argv[1]);
        smtp_s.sin_port = htons(atoi(argv[2]));

        if(connect(smtp_fd, (struct sockaddr *) &smtp_s, sizeof(smtp_s)) < 0) {
                fprintf(stderr, "Error connecting to %s\n", argv[1]);
                exit(-1);
        }
        bzero(buf, 256);
        bzero(rec_buf, 256);
        while(read(smtp_fd, rec_buf, 256) > 0 && (strstr(rec_buf, "220") != NULL || strstr(rec_buf, "250") != NULL || strstr(rec_buf, "354")) && seq < 6) {
                switch(seq) {
                        case 0 :
                                strcpy(buf, "HELO smtplib-0.1");
                                break;
                        case 1 :
                                 strcpy(buf, "MAIL FROM: ");
                                 strcat(buf, argv[3]);
                                 break;
                        case 2 :
                                 strcpy(buf, "RCPT TO: ");
                                 strcat(buf, argv[4]);
                                 break;
                        case 3 :
                                 strcpy(buf, "DATA");
                                 break;
                        case 4 :
                                 strcpy(buf, "X-Author: Krzysztof Krolikowski <kkrolikowski@gmail.com>\n");
                                 strcat(buf, "X-Mailer: smtp-lib-0.1\n");
                                 strcat(buf, "To: ");
                                 strcat(buf, argv[4]);
                                 strcat(buf, "\n");
                                 strcat(buf, "Subject: ");
                                 strcat(buf, argv[5]);
                                 strcat(buf, "\n\n");
                                 strcat(buf, argv[6]);
                                 strcat(buf, "\n.\n");
                                 break;
                        case 5 :
                                 strcpy(buf, "quit");
                                 break;
                }
                write(smtp_fd, buf, sizeof(buf));
                write(smtp_fd, "\r\n", 2);
                seq++;
        }
        close(smtp_fd);
        return 0;
}