Make socket send and receive more robust and return 0 on failure.

src/debug-agent.cc

Index: src/debug-agent.cc
diff --git a/src/debug-agent.cc b/src/debug-agent.cc
index 511663d8eeaab57c45639746e93c9ca1b3b6d049..a7015bfa206bb99f91728541fe98a225c69b6384 100644
--- a/src/debug-agent.cc
+++ b/src/debug-agent.cc
@@ -247,7 +247,7 @@ SmartArrayPointer<char> DebuggerAgentUtil::ReceiveMessage(const Socket* conn) {
     while (!(c == '\n' && prev_c == '\r')) {
       prev_c = c;
       received = conn->Receive(&c, 1);
-      if (received <= 0) {
+      if (received == 0) {
         PrintF("Error %d\n", Socket::LastError());
         return SmartArrayPointer<char>();
       }
@@ -454,7 +454,7 @@ int DebuggerAgentUtil::ReceiveAll(const Socket* conn, char* data, int len) {
   int total_received = 0;
   while (total_received < len) {
     int received = conn->Receive(data + total_received, len - total_received);
-    if (received <= 0) {
+    if (received == 0) {
       return total_received;
     }
     total_received += received;