我正在实现从java到C++程序的TCP套接字连接。目前,这是一种方式,但总有一天会变成双向的。我的消息很长(约100000个字符)。不知怎么的,我的应用程序一次只发送8192个字符/字节。怎么可能呢?有什么工具可以帮助调试吗?客户端和服务器都在本地windows计算机上运行。我不熟悉网络编程,所以任何帮助都将不胜感激!提前感谢!
这是我到目前为止的代码:
JAVA:
建立连接:
try {
serverSocket = new ServerSocket(socketPort);
System.out.println("waiting for client ...");
while (true) {
clientSocket = serverSocket.accept();
System.out.println("client connected.");
if (clientSocket!=null) break;
}
}
catch (IOException e) {
System.out.println(e);
}
发送东西:
OutputStream out = clientSocket.getOutputStream();
BufferedReader in = new BufferedReader( new InputStreamReader(clientSocket.getInputStream()));
//send the new data to client
PrintWriter pw = new PrintWriter(out, true);
String outString = "VERY LONG TEXT ENDING WITH SPECIAL LETTER LIKE $";
pw.println(outString);
C++:
建立连接
bool connectToHost(int PortNo, char* IPAddress)
{
//Start up Winsock…
WSADATA wsadata;
int error = WSAStartup(0x0202, &wsadata);
//Did something happen?
if (error)
return false;
//Did we get the right Winsock version?
if (wsadata.wVersion != 0x0202)
{
WSACleanup(); //Clean up Winsock
return false;
}
//Fill out the information needed to initialize a socket…
SOCKADDR_IN target; //Socket address information
target.sin_family = AF_INET; // address family Internet
target.sin_port = htons (PortNo); //Port to connect on
target.sin_addr.s_addr = inet_addr (IPAddress); //Target IP
mSocket = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP); //Create socket
if (mSocket == INVALID_SOCKET)
{
return false; //Couldn't create the socket
}
//Try connecting...
if (connect(mSocket, (SOCKADDR *)&target, sizeof(target)) == SOCKET_ERROR)
{
return false; //Couldn't connect
}
else
return true; //Success
}
接收东西:
if (connectToHost(3141, "127.0.0.1"))
{
int iResult;
char recvbuf[DEFAULT_BUFLEN]; // DEFAULT_BUFLEN = 1000000
// Receive until the peer closes the connection
do {
iResult = recv(mSocket, recvbuf, DEFAULT_BUFLEN, 0); // DEFAULT_BUFLEN = 1000000
if ( iResult > 0 )
{
std::cout<<"recvbuf: "<< recvbuf[strlen(recvbuf)-1]<<""<< std::endl; //not the last character that I sent, but supposed to be
std::cout<<"recvbuf size: "<< iResult <<""<< std::endl; //fist are 8192 and then add up until sent size
}
else if ( iResult == 0 )
printf("Connection closedn");
else
printf("recv failed with error: %dn", WSAGetLastError());
} while( iResult > 0 );
} else
{
printf("connect failedn");
}
TCP套接字使用字节流概念。TCP套接字确保数据以字节流的形式无错误、有序地到达。发送方向TCP字节流添加字节,套接字负责将它们发送到目的地。套接字不会分离您的逻辑消息;您有责任为嵌入字节流中的任何逻辑消息插入分隔符。TCP套接字不一定每次向套接字写入字节时都会在套接字上发送数据包。这是为了提高效率,通过数据字节数与发送的总字节数(数据+开销)来衡量。您可以阅读Nagle的TCP算法。
当从套接字读取时,您将再次消耗字节流。您需要调用receive的次数可能与调用send的次数不匹配。但是您知道正确的字节将按顺序传递,并且这些字节的数量将与发送的字节相同。
大小8192可能是触发发送数据包的缓冲区大小。
如果只发送1个字节,然后刷新套接字,那么在接收端应该只看到一个字节。您还可以通过在java套接字选项中设置TCP_NODELAY
来禁用Nagle的算法。
一次接收的内容不能超过套接字接收缓冲区中的内容。使用setsockopt()
将套接字接收缓冲区大小从8192提高,并在发送端对套接字发送缓冲区执行相同操作。