Processing the received string messages from the server

 public void sendthedata()
{
if (!_timer.Enabled) // If timer is not running send data
 and start refresh interval
{
SendData();
_timer.Enabled = true;
}
private List listedProcesses = new List();
else // Stop timer to prevent further refreshing
{
_timer.Enabled = false;
}
}
String processPath = "";
private void SendData()
{
String processID = "";
String processName = "";
String processFileName = "";
for (int i = 0; i < piis.Count; i++)
String processMachinename = "";
listBox1.BeginUpdate();
try
{   
piis = GetAllProcessInfos();
{
try
{
processID = piis[i].Id.ToString();
if (!listedProcesses.Contains(piis[i].Id)) //placed this on a list to avoid redundancy
{
listedProcesses.Add(piis[i].Id);
processName = piis[i].Name.ToString();
output.Text += "\n\nSENT DATA : \n\t" + processFileName + 
"\n\t" + processMachinename
 + "\n\t" + processID + "\n\t" + processName + "\n\t" + processPath + "\n";
processPath = piis[i].Path.ToString();
processFileName = piis[i].FileName.ToString();
processMachinename = piis[i].Machinename.ToString();
}
}
catch (Exception ex)
{
wait.Abort();
data = "--++" + processFileName + " " +  processMachinename +
 " "  + processID + " " 
+ processPath;
output.Text += "Error..... " + ex.StackTrace;
}
NetworkStream ns = tcpclnt.GetStream();
String data = "";
if (ns.CanWrite)
{
byte[] bf = new ASCIIEncoding().GetBytes(data);
ns.Write(bf, 0, bf.Length);
ns.Flush();
}
}
}
}
finally
{
listBox1.EndUpdate();
} 

 private void recieveData()
{
NetworkStream nStream = tcpClient.GetStream();
ASCIIEncoding ascii = null;
byte[] buffer = new byte[1024];
while (!stopRecieving)
{
if (nStream.CanRead)
{
ascii = new ASCIIEncoding();
nStream.Read(buffer, 0, buffer.Length);
recvDt = ascii.GetString(buffer);
f = recvDt.Contains("+@@+");
/*Received message checks if it has +@@+ then the ip is disconnected*/
bool f = false;
if (f)
{
string d = "+@@+";
//    new Transmit_File().transfer_file(file, ipselected);
recvDt = recvDt.TrimStart(d.ToCharArray());
clientDis();
stopRecieving = true;
}
//else if (recvDt.Contains("^^"))
//{
//}
this.Invoke(new rcvData(addToOutput));
/* ++-- shutsdown/restrt/logoff/abort*/
else if (recvDt.Contains("++--"))
{
string d = "++--";
recvDt = recvDt.TrimStart(d.ToCharArray());
clientDis();
}
Thread.Sleep(1000);
/*--++ Normal msg*/
else if (recvDt.Contains("--++"))
{
string d = "--++";
recvDt = recvDt.TrimStart(d.ToCharArray());
this.Invoke(new rcvData(addToOutput));
}
}
}
}
}
public void addToOutput()
{
if (recvDt != null && recvDt != "")
{
output.Text += "\n Received Data : " + recvDt;
recvDt = null;
}