> | # BSD TCP Client Sample ## Introduction This sample demonstrates how to write a TCP client application using the Berkeley Software Distribution (BSD) standard socket APIs to communicate with a SG15. For the purpose of this demonstration, the client application initiates communication with the SG15 by first creating a networking socket. Then using that socket, establishes a TCP connection to the SG15 and attempts to transmit and receive data from the SG15. ## SG15 Setup This sample was designed to operate with the SG15 operating in TCP Server mode. Configure the SG15 1. Use the SG15 configuration tool to access the settings of this specific SG15. 2. Choose the "Network" tab from the Configuration menu. 3. Check "TCP" and "Server" in the Connect Mode section. ## How To Build This sample has been compiled and tested using GCC 3.2 on Red Hat Linux 8.0. It contains a Makefile that is used for building the application. To build this sample 1. Change directory to where the sample source files reside. 2. Type make. ## Step-by-Step 1. Create a local socket The call to create a socket looks like this:
>     int Socket = socket(AF_INET, Type, Protocol);
> Where `Type` is `SOCK_STREAM` and `Protocol` is `IPPROTO_TCP` for a blocking, connection oriented TCP/IP socket. 2. Bind to a local port To bind the socket to a local port, call the following function:
>     bind(Socket, &SockAddr, sizeof(SockAddr));
> Binding to a local port must be done before using the socket to calls like `connect`, and is used to associate the currently unnamed socket with a local name. The `SockAddr` parameter is the `struct sockaddr` representation of the local name to bind to. This name consists of an address family (for TCP/IP, always `AF_INET`), a host address, and a port number. In this sample, the calls to `socket` and `bind` are both done in the function `MySocketOpen`. 3. Establish a connection Connections are established by calling the `connect` function.
>     connect(Socket, &SockAddr, sizeof(SockAddr));
> Where `SockAddr` is the `struct sockaddr` representation of the peer name to connect to. Because blocking sockets are being used, the call to `connect` will not return until the operation either fails or completes successfully. To simplify creating a connection, this sample uses a function named `MySocketConnect`.
>     MySocketConnect(MySocket,
>                     AddressToConnectTo,
>                     PortToConnectTo);
> Where `MySocket` is the socket returned from the call to `MySocketOpen`. `AddressToConnectTo` is a string that represents the IP address of the SG15 in dotted number format (e.g. "10.0.0.1"). `PortToConnectTo` is the port number used by the SG15 for raw TCP. On the SG15, this port number defaults to 9101. `MySocketConnect` hides the details of converting the IP address and port number to `struct sockaddr` representation. 4. Transmit data Transmitting data is done by calling `send`.
>     send(Socket, Data, Length, 0);
> After verifying the connection completed successfully, the sample uses the socket to transmit some data. For consistency the sample provides its own function named `MySocketSend`.
>     MySocketSend(MySocket, SendData, sizeof(SendData));
> The parameters needed for `MySocketSend` are: `MySocket` which is the socket returned from `MySocketOpen`, `SendData` which is a pointer to the buffer holding the data to send, and `sizeof(SendData)` which is the number of bytes `SendData` points to. 5. Receive data To retrieve data received at the local address, call `recv`.
>     recv(Socket, Data, Length, 0);
> Again for consistency, the sample provides its own function, `MySocketRecv`
>     MySocketRecv(MySocket, RecvData, sizeof(RecvData));
> The caller to `MySocketRecv` must supply the prerequisite `MySocket`, a buffer `RecvData` to hold the received data, and `sizeof(RecvData)` which specifies the length of `RecvData`. 6. Close the socket Accomplish this task by calling the following two functions:
>     shutdown(Socket, SHUT_RDWR);
>     close(Socket);
When the sample application is done using the socket, the connection it represents must be terminated properly (`shutdown`) and any resources it may be using should be released (`close`). ## File List hexdumpdata.cpp hexdumpdata.h Makefile mysocket.cpp mysocket.h tcpclient.cpp ## Keywords socket; bind; connect; send; recv; shutdown; close
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