Complete some error handling when send or receive function returns a value is zero.

examples/network/tcpserver.c

@@ -9,6 +9,7 @@ void tcpserv(void* parameter)
    int sock, connected, bytes_received;
    struct sockaddr_in server_addr, client_addr;
    rt_bool_t stop = RT_FALSE; /* 停止标志 */
+   int ret;
 
    recv_data = rt_malloc(1024); /* 分配接收用的数据缓冲 */
    if (recv_data == RT_NULL)
@@ -72,16 +73,31 @@ void tcpserv(void* parameter)
        while (1)
        {
            /* 发送数据到connected socket */
-           send(connected, send_data, strlen(send_data), 0);
-
+           ret = send(connected, send_data, strlen(send_data), 0);
+		   if (ret < 0)
+		   {
+				/* 接收失败，关闭这个连接 */
+				lwip_close(sock);
+				rt_kprintf("\nsend error,close the socket.\r\n");		
+				break;
+		   }else if (ret == 0)
+		   {
+				/* 打印send函数返回值为0的警告信息 */
+				rt_kprintf("\n Send warning,send function return 0.\r\n");						
+		   }		
+		   
            /* 从connected socket中接收数据，接收buffer是1024大小，但并不一定能够收到1024大小的数据 */
            bytes_received = recv(connected,recv_data, 1024, 0);
-           if (bytes_received <= 0)
+           if (bytes_received < 0)
            {
                /* 接收失败，关闭这个connected socket */
                lwip_close(connected);
                break;
-           }
+           }else if (bytes_received == 0)
+		   {
+			   /* 打印recv函数返回值为0的警告信息 */
+			   rt_kprintf("\nReceived warning,recv function return 0.\r\n");						
+		   }
 
            /* 有接收到数据，把末端清零 */
            recv_data[bytes_received] = '\0';