Java服务器套接字
在以下代码中: https://docs.oracle.com/javase/tutorial/networking/sockets/examples/KnockKnockServer.java
import java.net.*;
import java.io.*;
public class KnockKnockServer {
public static void main(String[] args) throws IOException {
if (args.length != 1) {
System.err.println("Usage: java KnockKnockServer <port number>");
System.exit(1);
}
int portNumber = Integer.parseInt(args[0]);
try (
ServerSocket serverSocket = new ServerSocket(portNumber);
Socket clientSocket = serverSocket.accept();
PrintWriter out =
new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
) {
String inputLine, outputLine;
// Initiate conversation with client
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
} catch (IOException e) {
System.out.println("Exception caught when trying to listen on port "
+ portNumber + " or listening for a connection");
System.out.println(e.getMessage());
}
}
}
当服务器将其响应发送到客户端套接字时,它使用“println()”方法(第63行)写入“PrintWriter”“out”。
EOF
,CR LF
(在我的情况下)(10和13个ASCII字符)?的Winsock
在以下代码中: http://msdn.microsoft.com/en-us/library/windows/desktop/ms737591%28v=vs.85%29.aspx
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
// Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(int argc, char **argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char *sendbuf = "this is a test";
char recvbuf[DEFAULT_BUFLEN];
int iResult;
int recvbuflen = DEFAULT_BUFLEN;
// Validate the parameters
if (argc != 2) {
printf("usage: %s server-name\n", argv[0]);
return 1;
}
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
ZeroMemory( &hints, sizeof(hints) );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
// Resolve the server address and port
iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
if ( iResult != 0 ) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Attempt to connect to an address until one succeeds
for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
WSACleanup();
return 1;
}
// Connect to server.
iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
break;
}
freeaddrinfo(result);
if (ConnectSocket == INVALID_SOCKET) {
printf("Unable to connect to server!\n");
WSACleanup();
return 1;
}
// Send an initial buffer
iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
printf("Bytes Sent: %ld\n", iResult);
// shutdown the connection since no more data will be sent
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Receive until the peer closes the connection
do {
iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
if ( iResult > 0 )
printf("Bytes received: %d\n", iResult);
else if ( iResult == 0 )
printf("Connection closed\n");
else
printf("recv failed with error: %d\n", WSAGetLastError());
} while( iResult > 0 );
// cleanup
closesocket(ConnectSocket);
WSACleanup();
return 0;
}
使用“send()”方法。
当一个“消息”(一个字符数组)从一个套接字端点发送到另一个套接字端点时,该消息是否必须以某种EOF结束?现在我觉得它没有。
答案 0 :(得分:1)
一般不需要在Java套接字通信中发送EOF标志,但是
如果您的客户端使用InputStream.readLine()来读取服务器的答案,那么这是正常的,因为
readLine()阻塞,直到完全读取一行(直到找到\ n \ r或\ r \ n)或服务器关闭套接字。
但在此示例中,服务器未关闭套接字,因为服务器正在等待客户端应答,如果客户端正在等待行结束,则会出现死锁。
答案 1 :(得分:1)
当服务器将其响应发送到客户端套接字时,它会写入&#34; PrintWriter&#34; &#34;列&#34;使用&#34; println()&#34;方法
PrintWriter
是行缓冲的。见Javadoc。
我尝试过使用&#34; print()&#34;方法改为。
如果你不写一条线,它就不会冲洗。之后致电flush()
。但是你不应该在网络上使用PrintWriter
,因为它会吞下您需要了解的异常。使用BufferedWriter
。
在&#34; println()&#34; case,客户端套接字正确接收消息。
因为它是行缓冲的,所以有一个自动刷新。
在&#34; print()&#34;如果客户端套接字没有收到任何内容。
因为它是行缓冲的,所以没有自动刷新。
这是正常的吗?
是
是否需要在邮件末尾发送EOF,CR LF(在我的情况下)(10和13个ASCII字符)?
没有
是否记录在某处?
是的,在PrintWriter
的Javadoc中。