如何连接到邮件服务器用C [英] How to connect to mail server in C
本文介绍了如何连接到邮件服务器用C的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我试图让我的邮件服务器的连接是在局域网。邮件服务器的IP为192.168.1.1。于是,我尝试了
下面的程序来测试。
I tried to make a connection to my mail server which is in local area network. The ip of mail server is 192.168.1.1. So, I tried the following program to test that.
程序:
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
int main()
{
struct sockaddr_in sa;
struct in_addr ip;
int fd=socket(AF_INET,SOCK_STREAM,0);
if(inet_pton(AF_INET,"192.168.1.1",&ip)==-1){
printf("Unable to convert ip to binary\n");
perror("");
exit(1);
}
sa.sin_family=AF_INET;
sa.sin_port=25;
sa.sin_addr=ip;
if(connect(fd,(struct sockaddr*)&sa,sizeof(sa))==-1){
printf("Unable to connect to server\n");
perror("");
exit(1);
}
else{
printf("Successfully connected to server...\n");
}
}
输出:
$ ./a.out
Unable to connect to server
Connection refused
$
但是通过telnet,它被成功连接,如下所示。
But via telnet, it is successfully connected as shown below.
$ telnet 192.168.1.1 25
Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.
220 mail.msys.co.in ESMTP Postfix (Debian/GNU)
^]
telnet> Connection closed.
$
那么,什么是我在这里完成的错误。这有什么错在我的计划。我请求你帮我解决这个问题,为什么它会发生。
So, what is the mistake I done here. Is there anything wrong in my program. I request you to help me solve this problem and why it occurs.
推荐答案
随着Wireshark的跟踪,你可以看到你的code试图连接到端口6400尝试:
With a wireshark trace you can see that your code tries to connect to port 6400. Try:
sa.sin_port = htons(25);
sa.sin_port=htons(25);
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