sockets - How to connect to mail server in C -

i tried make connection mail server in local area network. ip of mail server 192.168.1.1. so, tried following program test that.

program:

#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 convert ip 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 connect server\n");         perror("");         exit(1);     }     else{         printf("successfully connected server...\n");     } } 

output:

$ ./a.out  unable connect server connection refused $ 

but via telnet, connected shown below.

$ telnet 192.168.1.1 25 trying 192.168.1.1... connected 192.168.1.1. escape character '^]'. 220 mail.msys.co.in esmtp postfix (debian/gnu) ^] telnet> connection closed. $ 

so, mistake done here. there wrong in program. request me solve problem , why occurs.

with wireshark trace can see code tries connect port 6400. try:

sa.sin_port=htons(25);