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java.net.BindException: Permission denied when creating a ServerSocket on Mac OSX

I Tried to run a Java socket in mac with eclipse but it doesn't work. I got this error:
Exception in thread "main" java.net.BindException: Permission denied
at java.net.PlainSocketImpl.socketBind(Native Method)
at java.net.PlainSocketImpl.socketBind(PlainSocketImpl.java:521)
at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:414)
at java.net.ServerSocket.bind(ServerSocket.java:326)
at java.net.ServerSocket.<init>(ServerSocket.java:192)
at java.net.ServerSocket.<init>(ServerSocket.java:104)
at server.MessageServer.main(MessageServer.java:11)
How can i make it to run?
package server; //ChatServer
import java.io.*;
import java.net.*;
public class MessageServer {
public static void main (String args[]) throws IOException {
int port = 100;
ServerSocket server = new ServerSocket (port);
System.out.println("Server is started!");
while (true) {
Socket client = server.accept ();
System.out.println ("Accepted from " + client.getInetAddress ());
MessageHandler handler = new MessageHandler (client);
handler.start();
}
}
}

You can't open a port below 1024, if you don't have root privileges and from the code you posted in your comment, you seem to be trying to open port 100 which confirms my theory.
You need to use a port which is higher than 1024, if you're running the code under a non-root user.

Unix-based systems declare ports < 1024 as "privileged" and you need admin rights to start a server.
For testing, use a port number >= 1024.
When deploying the server in production, run it with admin rights.

I had the same issue and my port numbers were below 1024 changing port number to above 1024 solved my problem. Ports below 1024 are called Privileged Ports and in Linux (and most UNIX flavors and UNIX-like systems), they are not allowed to be opened by any non-root user.

Many systems declare ports that are less than 1024 as "admin rights" ports. Meaning, if you're only using this for basic testing use a higher port such as 2000. This will clear the exception that you're getting by running your current program.
int port = 100;
ServerSocket server = new ServerSocket (port);
Change that to something such as:
int port = 2000;
ServerSocket server = new ServerSocket (port);

MyServer.java
import java.io.*;
import java.net.*;
public class MyServer
{
ServerSocket ss;
Socket s;
DataOutputStream dos;
DataInputStream dis;
public MyServer()
{
try
{
System.out.println("Server Started ");
ss=new ServerSocket(4444);
s=ss.accept();
System.out.println(s);
System.out.println("Client Connected");
dis=new DataInputStream(s.getInputStream());
dos=new DataOutputStream(s.getOutputStream());
ServerChat();
}
catch(Exception e)
{
System.out.println(e);
}
}
public static void main(String arg[])
{
new MyServer();
}
public void ServerChat()throws IOException
{
String str;
do
{
str=dis.readUTF();
System.out.println("Client msg : "+str);
dos.writeUTF("Hello "+str);
dos.flush();
}while(!str.equals("stop"));
}
}
MyClient.java
import java.io.*;
import java.net.*;
public class MyClient
{
Socket s;
DataInputStream din;
DataOutputStream dout;
public MyClient()
{
try
{
s=new Socket("localhost",4444);
System.out.println(s);
din = new DataInputStream(s.getInputStream());
dout = new DataOutputStream(s.getOutputStream());
ClientChat();
}
catch(Exception e)
{
System.out.println(e);
}
}
public void ClientChat() throws IOException
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String s1;
do
{
s1=br.readLine();
dout.writeUTF(s1);
dout.flush();
System.out.println("Server Msg : "+din.readUTF());
}while(!s1.equals("stop"));
}
public static void main(String arg[])
{
new MyClient();
}
}

Run Server program with root (Administrator).
Windows: Run as Administrator the IDE/Editor.
Ubuntu/macOS: sudo java...

This is an old question, and I might be replying too late, but I would like to anyways share my experience in case anyone hits the issue.
I was using port# 8000, but still unable to bind to the port from a java program. It was network filter running as part of eset endpoint security that was blocking the connection.
I added a rule in eset firewall to allow port 8000, and it started working.

Running Socket Programming code in Eclipse

I have written a program on Socket Programming, and I created a client and a server. Codes for both are as follows:
CLIENT:
import java.net.*;
import java.io.*;
public class GreetingClient
{
public static void main(String [] args)
{
String serverName = args[0];
int port = Integer.parseInt(args[1]);
try
{
System.out.println("Connecting to " + serverName
+ " on port " + port);
Socket client = new Socket(serverName, port);
System.out.println("Just connected to "
+ client.getRemoteSocketAddress());
OutputStream outToServer = client.getOutputStream();
DataOutputStream out =
new DataOutputStream(outToServer);
out.writeUTF("Hello from "
+ client.getLocalSocketAddress());
InputStream inFromServer = client.getInputStream();
DataInputStream in =
new DataInputStream(inFromServer);
System.out.println("Server says " + in.readUTF());
client.close();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
SERVER:
import java.net.*;
import java.io.*;
public class GreetingServer extends Thread
{
private ServerSocket serverSocket;
public GreetingServer(int port) throws IOException
{
serverSocket = new ServerSocket(port);
serverSocket.setSoTimeout(10000);
}
public void run()
{
while(true)
{
try
{
System.out.println("Waiting for client on port " +
serverSocket.getLocalPort() + "...");
Socket server = serverSocket.accept();
System.out.println("Just connected to "
+ server.getRemoteSocketAddress());
DataInputStream in =
new DataInputStream(server.getInputStream());
System.out.println(in.readUTF());
DataOutputStream out =
new DataOutputStream(server.getOutputStream());
out.writeUTF("Thank you for connecting to "
+ server.getLocalSocketAddress() + "\nGoodbye!");
server.close();
}catch(SocketTimeoutException s)
{
System.out.println("Socket timed out!");
break;
}catch(IOException e)
{
e.printStackTrace();
break;
}
}
}
public static void main(String [] args)
{
int port = Integer.parseInt(args[0]);
try
{
Thread t = new GreetingServer(port);
t.start();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
Now, I am unable to run the program in Eclipse, can anyone help me, how to do this ?

Go to RunConfigurations.. and click on the Class Name(as here 'GreetingClient') under the java application in the left pane of RunConfiguration window
on the right side you will get many tab like Main,Arguments,jre,ClassPath etc so now click on the 'Arguments'
below this tag you will get textbox with label Program arguments:
here in this textbox you need to pass your command line argument
for multiple values give single space between the argument values then click on the Apply button
like in above case you need to pass commandline argument twice.
so first you configure for the GreetingServer and then for the GreetingClient and then apply and run one by one
click on the GreetingServer.java and then right click on mouse and select Run As-->Run Configuration.. then go to Java Application and click
GreetingServer -->Argument--> 6000 -->apply and -->run
output like this
Waiting for client on port 6000...
now click on the GreetingClient.java and then right click on mouse and select Run As-->Run Configuration.. then go to Java Application and click
GreetingClient -->Argument--> 127.0.0.1 6000 -->apply and -->run
then you will get your application running and
output like this
Connecting to 127.0.0.1 on port 6000
Just connected to /127.0.0.1:6000
Server says Thank you for connecting to /127.0.0.1:6000
Goodbye!
Any port you can send it your wise just keep in mind port no. should be free
for the eclipse argument passing you can go through this link

Actually, you need to run the programs individually in the
Eclipse-IDE. The output will be indented one on another in next tab on
the output area.
I don't have info about Eclipse.
In Netbeans,you need to run the Client.java file separately. Then,move
to Server.java file and run it separately. You'll see at the bottom
that two windows---one running Client.java and the other running
Server.java will be running independently. Now,send message from
client to server and vice-versa.
EDIT FOR YOUR COMMAND LINE PARAMETER SETTING IN ECLIPSE IDE :-
Go to Project--> Run --> Run Configurations --> Arguments.!
Pass the arguments as
args[0]=127.0.0.1 //local-host
args1=3000 //say 3000,you can give any port no. but take care that it should exist!

Try running the Client program first and then run the server program in Netbeans, the program will run with no problem...

/*Server*/
import java.net.*;
import java.io.*;
public class MyServer
{
public static void main(String args[])throws Exception
{
ServerSocket ss=new ServerSocket(8100);
Socket s=ss.accept();
DataInputStream din=new DataInputStream(s.getInputStream());
DataOutputStream dout=new DataOutputStream(s.getOutputStream());
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String str="",str2="";
while(!str.equals("stop"))
{
str=din.readUTF();
System.out.println("clint Says"+str);
str2=br.readLine();
dout.writeUTF(str2);
dout.flush();
}
din.close();
s.close();
ss.close();
}
}

Creating a simple internet chat

I tried to create a simple chat via sockets and it works for LAN right now and for "localhost" too, of course, but not among different computers through the internet and thats the real point of a chat, isn't it!
socket = new Socket("--ip address--", 7345);
This line works for --ip address-- = localhost and --ip address-- = ""my local ip-address"", but with the ip address of my router, it throws a java.net.ConnectException
" java.net.ConnectException: Connection refused: connect "
I want to use my pc as server and not a real server, maybe there is the problem, but I think that there must be a solution. If that is an absurd simple question, don't doom me, because I'm a real newbie in network programming.

When you are creating a server, you have to use server socket with the ip address of where it's running...
The server socket needs to be running on your machine of your machine's ip address.
With your router, you need to forward the connections to the port you are running on your that is hosting the server.
Then you should be able to connect from outside your local network.
Without the code for what your are doing it's hard to tell if that's the only problem here is a simple chat server that might give you guidance.
import java.net.*;
import java.io.*;
public class ChatServer
{ private Socket socket = null;
private ServerSocket server = null;
private DataInputStream streamIn = null;
public ChatServer(int port)
{ try
{
System.out.println("Binding to port " + port + ", please wait ...");
server = new ServerSocket(port);
System.out.println("Server started: " + server);
System.out.println("Waiting for a client ...");
socket = server.accept();
System.out.println("Client accepted: " + socket);
open();
boolean done = false;
while (!done)
{ try
{ String line = streamIn.readUTF();
System.out.println(line);
done = line.equals(".bye");
}
catch(IOException ioe)
{
done = true;
}
}
close();
}
catch(IOException ioe)
{ System.out.println(ioe);
}
}
public void open() throws IOException
{ streamIn = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
}
public void close() throws IOException
{ if (socket != null) socket.close();
if (streamIn != null) streamIn.close();
}
public static void main(String args[])
{ ChatServer server = null;
if (args.length != 1)
System.out.println("Usage: java ChatServer port");
else
server = new ChatServer(Integer.parseInt(args[0]));
}
}

Trying to get a java socket program to work, but getting "java.net.BindException: Address already in use 6666 "

Here is the code
I have written a server and client. But when i run them, (as you can see in the last program), I get the following error:
Whoop s! java.net.BindException: Address already in use 6666
6666 is the port no. i specified.
import java.net.*;
import java.io.*;
import java.lang.*;
public class processSendHelper
{
Process p;
String address;
int port;
long msg_data;
processSendHelper(int pid, int current_round, long address, long msg_data, int port)
{
try
{
ServerSocket sSoc = new ServerSocket(port);
Socket inSoc = sSoc.accept();
msg_Thread msgT = new msg_Thread(inSoc, msg_data);
msgT.start();
Thread.sleep(5000);
sSoc.close();
}
catch(Exception e)
{
System.out.println("Whoop s! " + e.toString());
}
}
}
/* sends out (or rather just makes available) the provided msg
* */
class msg_Thread extends Thread
{
Socket threadSoc;
long msg_data;
msg_Thread (Socket inSoc, long msg_data)
{
threadSoc = inSoc;
this.msg_data = msg_data;
}
public void run()
{
try
{
PrintStream SocOut = new
PrintStream(threadSoc.getOutputStream());
SocOut.println(msg_data);
}
catch (Exception e)
{
System.out.println("Whoops!" + e.toString());
}
try
{
threadSoc.close();
}
catch (Exception e)
{
System.out.println("Oh no! " +
e.toString());
}
}
}
import java.net.*;
import java.io.*;
public class processReceiveHelper
{
Socket appSoc;
BufferedReader in;
String message;
String host;
int port;
processReceiveHelper(String host,int port)
{
try
{
appSoc = new Socket(host,port);
in = new BufferedReader(new InputStreamReader(appSoc.getInputStream()));
message = in.readLine();
System.out.println(message);
/* Tokenizer code comes here
* Alongwith the code for
* updating the process object's
* data
* */
}
catch (Exception e)
{
System.out.println("Died... " +
e.toString());
}
}
}
public class Orchestrator
{
public static void main(String[] args)
{
processSendHelper psh = new processSendHelper(1, 2, 1237644, 6666, 2002);
processReceiveHelper prh = new processReceiveHelper("localhost", 2002);
}
}
EDIT:
I found the problem. The reason was that i was running both the server and client from the same main program.
the following worked:

That means there is already an application operating on port 6666 preventing your Java application using it. However, it is equally possible there is a running process of your Java application still holding onto 6666. Terminate any running java processes and try re-running the code - if it still fails then you have some other application using 6666 and you would be better using a different port.

That means that the port 6666 is already being used. There are two main causes/solutions for this:
Some other program is using that port. Solution: Choose a different port.
Your old Java program is hanging and still "using" that port. Close all of your hanging Java programs and try again. If that doesn't solve your problem, choose a different port.

Does it happen when you run the program for the second time? You may want to setReuseAddress(true) on this socket.

Multiple non-simultaneous Java client-server connections using always the same port

I'm trying to test a scenario where one server accepts connections(one each time) from one client, using always the same ports (on the server and on the client side).
The purpose is to have 1 client application sending little pieces of data at a rate bigger than 100/min. The well obvious solution would be to have an always connected link between the client and the server, but this is production stuff, and that would require bigger changes in the code that is already implemented. With the solution we have implemented today, we always have +-1K of connections in TIME_WAIT, and I want to get rid of them.
I have implemented a simple tester, and the code is:
public class Server {
public static void main(String[] args) {
ServerSocket ssock = null;
try {
ssock = new ServerSocket();
ssock.bind(new InetSocketAddress(Common.SERVER_PORT));
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
while(true){
try{
Socket cSock = ssock.accept();
BufferedReader reader = new BufferedReader(new InputStreamReader(cSock.getInputStream()));
reader.readLine();
PrintWriter writer = new PrintWriter(cSock.getOutputStream());
writer.println(Common.SERVER_SEND);
writer.flush();
reader.close();
writer.close();
cSock.close();
}catch (Exception e) {
System.out.println(e.getClass().getName() + ": " + e.getMessage());
}
}
}
}
public class Client {
public static void main(String[] args) throws Exception {
InetSocketAddress cliAddr = new InetSocketAddress(
InetAddress.getByName(args[0]),
Common.CLIENT_PORT);
InetSocketAddress srvAddr = new InetSocketAddress(
InetAddress.getByName(args[1]),
Common.SERVER_PORT);
for(int j=1;j<=50;j++){
Socket sock = null;
try{
sock = new Socket();
sock.setReuseAddress(true);
sock.bind(cliAddr);
sock.connect(srvAddr);
PrintWriter writer =
new PrintWriter(
sock.getOutputStream());
writer.println(Common.CLIENT_SEND);
writer.flush();
BufferedReader reader =
new BufferedReader(
new InputStreamReader(
sock.getInputStream()));
reader.readLine();
}catch (Exception e) {
System.out.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(-1);
}finally{
if(sock!=null) sock.close();
System.out.println("Done " + j);
}
}
}
}
public class Common {
public static final int SERVER_PORT = 9009;
public static final int CLIENT_PORT = 9010;
public static final String CLIENT_SEND = "Message";
public static final String SERVER_SEND = "OK";
}
When executing the client and server, on windows hosts, in one client execution I always get
java.net.ConnectException: Connection timed out
When executing the client and the server in linux hosts, on some client executions I get a
java.net.NoRouteToHostException: Cannot assign requested address
I've been killing my head over this behavior. Can someone please tell me if it is possible to do what I want, and what I am doing wrong?

If you want to get rid of the TIME_WAIT state, don't be the peer that receives the close. Be the peer that initiates the close. In this case, close the connection immediately after reading the response, and have the server cycle around looking for another request so that it reads the EOF rather than just closing the connection immediately after sending the response. However this will only make the problem worse, as all the TIME_WAIT states will accumulate at the server rather than at the client. On the other hand, the server is now structured to accept multiple requests per connection, so then all you have to do is adapt the clients to use a connection pool and all your problems are solved.