I am building a simple mail client for the google mail server "smtp.gmail.com" on port 25 using JAVA socket connections as a school project. The initiation and connection to the server are done well. But when it comes to authenticating after issuing a "STARTTLS" command, I am getting a weird reply and sometimes no reply from the server. The following is the portion of my code responsible for this error:
public class Client {
public static void main(String[] args) throws IOException {
System.out.println("Connecting to server...");
Socket cs = new Socket("smtp.gmail.com", 25);
System.out.println("Connected to server! via port: " + cs.getLocalPort());
OutputStreamWriter osw = new OutputStreamWriter(cs.getOutputStream());
InputStreamReader isr = new InputStreamReader(cs.getInputStream());
BufferedWriter bw = new BufferedWriter(osw);
char[] inputBuffer = new char[1024];
int len = isr.read(inputBuffer);
String s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + s);
System.out.println("C: HELO localhost");
bw.write("HELO localhost");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + s);
System.out.println("C: STARTTLS");
bw.write("STARTTLS");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + s);
System.out.println("C: EHLO localhost");
bw.write("EHLO localhost");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + s);
System.out.println("C: AUTH LOGIN");
bw.write("AUTH LOGIN");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + s);
// extra code goes here, no need to show
}
}
The following is the output:
Connecting to server...
Connected to server! via port: 39167
S: 220 smtp.gmail.com ESMTP v52sm3768873wrc.53 - gsmtp
C: HELO localhost
S: 250 smtp.gmail.com at your service
C: STARTTLS
S: 220 2.0.0 Ready to start TLS
C: EHLO localhost
S: F
C: AUTH LOGIN
S:
As you may see, the reply to "EHLO localhost" after "STARTTLS" is ambiguous, and then no reply for "AUTH LOGIN". I first thought that it should be that the server is sending Base64 text, so I tried to decode the response as follows:
System.out.println("C: EHLO localhost");
bw.write("EHLO localhost");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + new String(Base64.getDecoder().decode(s)));
System.out.println("C: AUTH LOGIN");
bw.write("AUTH LOGIN");
bw.newLine();
bw.flush();
len = isr.read(inputBuffer);
s = "";
for(int i = 0; i < len; ++i){
s += inputBuffer[i];
}
System.out.println("S: " + new String(Base64.getDecoder().decode(s)));
But the following error is obtained:
Connecting to server...
Connected to server! via port: 39199
S: 220 smtp.gmail.com ESMTP l27sm4475707wrb.65 - gsmtp
C: HELO localhost
S: 250 smtp.gmail.com at your service
C: STARTTLS
S: 220 2.0.0 Ready to start TLS
C: EHLO localhost
Exception in thread "main" java.lang.IllegalArgumentException: Illegal base64 character 15
at java.util.Base64$Decoder.decode0(Unknown Source) at java.util.Base64$Decoder.decode(Unknown Source) at java.util.Base64$Decoder.decode(Unknown Source) at khaldoun.kassam.servertest.Client.main(Client.java:64)
I thought that maybe I should use SSLSockets but from what I see is that some people were able to use the normal Sockets and it worked for them. I searched a lot for this problem without any result. I don't know if something is missing in the sent commands to the server. I really need help. Thank you in advance for your time.
