Using Concatenate strings to communicate to a client

I got the server to send name of chat user along with message ex: sname> "message" but for some reason im getting weird symbols after sname> is received... Can someone see where i can improve this code

Code:

/* chatserver.c */


#include <stdlib.h>
#include <stdio.h>
#include "cnaiapi.h"


#define BUFFSIZE        128
#define MAX_SNAME                10


int recvln(connection, char *, int);
int readln(char *, int);


void concatenate_strings (char *source, int source_len, char *dest, int dest_len)
{    int i;
    for(i=0; i<dest_len; i++){
        source[source_len + i] = dest[i]; }
    source[source_len + dest_len] = NULL;
}


/*-----------------------------------------------------------------------
 *
 * Program: chatserver
 * Purpose: wait for a connection from a chatclient & allow users to chat
 * Usage:   chatserver <appnum>
 *
 *-----------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
    connection    conn;
    int        len;
    char        buff[BUFFSIZE];
      char            sname[MAX_SNAME];




    if (argc != 2) {
        (void) fprintf(stderr, "usage: %s <appnum>\n", argv[0]);
        exit(1);
    }


    
    /* Input Name to use */


    printf ("Enter your chat name. \n");
    len = readln( sname, MAX_SNAME);


    /* To add the ">" after the name */
    sname[len -1] ='>';
    sname[len] = NULL;  
    


    (void) printf("Chat Server Waiting For Connection.\n");
 
    


    /* wait for a connection from a chatclient */


    conn = await_contact((appnum) atoi(argv[1]));
    if (conn < 0)
        exit(1);
    
    (void) printf("Chat Connection Established.\n");
    
    /* iterate, reading from the client and the local user */


    while((len = recvln(conn, buff, BUFFSIZE)) > 0) {
        (void) fflush(stdout);
        (void) write(STDOUT_FILENO, buff, len);
        
        /* send a line to the chatclient */


        printf (sname);
    
        (void) fflush(stdout);
        if ((len = readln(buff, BUFFSIZE+MAX_SNAME)) < 1)   
            break;
        buff[len - 1] = '\n';
        concatenate_strings (sname, MAX_SNAME, buff, BUFFSIZE);
        printf (sname);
        (void) send(conn, sname, MAX_SNAME+BUFFSIZE, 0);                
    }


      /* iteration ends when EOF found on stdin or chat connection */


    (void) send_eof(conn);
    (void) printf("\nChat Connection Closed.\n\n");
    return 0;
}

My answer is over there -> Sending A Concatenated string - Dev Shed

Stop with the spamming already!
Sending A Concatenated string