client.c

    #include <stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <sys/un.h>
    
    #define SOCK_PATH "/tmp/test.sock"
    
    int main(void) {
      int s, t, len;
      struct sockaddr_un remote;
      char str[100];
    
      if ((s = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
      }
    
      printf("Trying to connect...\n");
    
      remote.sun_family = AF_UNIX;
      strcpy(remote.sun_path, SOCK_PATH);
      len = strlen(remote.sun_path) + sizeof(remote.sun_family);
      if (connect(s, (struct sockaddr *)&remote, len) == -1) {
        perror("connect");
        exit(1);
      }
    
      printf("Connected.\n");
    
      while(printf("> "), fgets(str, 100, stdin), !feof(stdin)) {
        if (send(s, str, strlen(str)-1, 0) == -1) {
          perror("send");
          exit(1);
        }
    
        if ((t=recv(s, str, 100, 0)) > 0) {
          str[t] = '\0';
          printf("echo> %s", str);
        } else {
          if (t < 0) perror("recv");
          else printf("Server closed connection\n");
          exit(1);
        }
      }
    
      close(s);
      return 0;
    }

output

    $ node -v
    v0.1.98-5-g02da5ed

    $ node server.js
    unix socket open: /tmp/test.sock

In another terminal:

    $ gcc -o client client.c
    $ ./client
    Trying to connect...
    Connected.
    > hi

In first terminal:

    server got: hi
    server got: hi
    server got: hi
    server got: hi
    server got: hi
    server got: hi
    server got: hi
    ^C

server.js

    #!/usr/bin/env node
    
    var sys = require('sys'),
        dgram = require("dgram"),
        sock_path = '/tmp/test.sock';
    
    var server = dgram.createSocket(function (msg) {
      sys.puts("server got: " + msg);    // msg is a Buffer
      server.send(sock_path, null, msg);
    });
    
    server.addListener("error", function (e) {
      sys.error('got an error: ' + e);
      throw e;
    });
    
    server.addListener("listening", function () {
      sys.puts("unix socket open: " + sock_path);
    });
    
    server.addListener("close", function (e) {
      sys.puts("unix socket closed: " + sock_path);
    });
    
    server.bind(sock_path);
    
    [ 'SIGTERM', 'SIGINT', 'SIGKILL', 'SIGQUIT' ].forEach(function (sig) {
      process.addListener(sig, function () {
        sys.puts(sig + ": closing unix socket");
        server.close();
      });
    });

test-dgram-pingpong.js.diff

diff --git a/test/simple/test-dgram-pingpong.js b/test/simple/test-dgram-pingpong.js
index 61a736a..070d32a 100644
--- a/test/simple/test-dgram-pingpong.js
+++ b/test/simple/test-dgram-pingpong.js
@@ -14,11 +14,11 @@ function pingPongTest (port, host) {
 
     puts("server got: " + msg);
 
-    if (/PING/.exec(msg)) {
+//    if (/PING/.exec(msg)) {
       var buf = new Buffer(4);
       buf.write('PONG');
-      server.send(rinfo.port, rinfo.address, buf, 0, buf.length);
-    }
+      server.send(port /*rinfo.port*/, rinfo.address, buf, 0, buf.length);
+//    }
 
   });
 
@@ -71,11 +71,11 @@ function pingPongTest (port, host) {
 }
 
 /* All are run at once, so run on different ports */
+pingPongTest("/tmp/pingpong.sock");
 pingPongTest(20989, "localhost");
 pingPongTest(20990, "localhost");
 pingPongTest(20988);
 pingPongTest(20997, "::1");
-//pingPongTest("/tmp/pingpong.sock");
 
 process.addListener("exit", function () {
   assert.equal(4, tests_run);