我有一个用C编写的TCP / IP服务器程序和一个用Java编写的相应客户端：
C服务器
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#include <netdb.h>
#define PORT 0
int main(int argc, char *argv[]) {
printf("ISV_APP: Initiating TCP/IP networking.\n");
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
char buffer[1024] = {0};
// Creating socket file descriptor.
if((server_fd = socket(AF_INET, SOCK_STREAM,0)) == 0)
{
printf("TCP/IP: Initiation of server socket file descriptor failed.\n" );
return -1;
}
printf("TCP/IP: Initializing server socket.\n" );
// Forcefully attaching socket to the connection port.
if(setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt)))
{
printf("TCP/IP: Error with setsockopt call occured.\n" );
return -1;
}
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(PORT);
printf("TCP/IP: Socket options have been set.\n" );
// Binding the socket.
if(bind(server_fd, (struct sockaddr *)&address, sizeof(address)) <0){
printf("TCP/IP: Failed to bind socket.\n" );
return -1;
}
printf("TCP/IP: Socket bound to port.\n" );
// Listen for connections
if(listen(server_fd, 3) < 0){
printf("TCP/IP: Failed to listen for incoming connections.\n" );
return -1;
}
// Print the assigned port and address so that client knows how to connect.
struct sockaddr_in sin;
socklen_t len = sizeof(sin);
if (getsockname(server_fd, (struct sockaddr *)&sin, &len) == -1){
printf("Failed to read port number.\n" );
}
else{
// Print port
unsigned int my_port = ntohs(sin.sin_port);
char my_port_str[6];
sprintf(my_port_str, "%d", my_port);
printf("\nINFO: Socket bound to port: " );
printf(my_port_str);
printf("\n");
// Print address
char my_ip[16];
inet_ntop(AF_INET, &sin.sin_addr, my_ip, sizeof(my_ip));
printf("INFO: Server IP Address: ");
printf(my_ip);
printf("\n");
printf("\nServer is listening for incoming connections...\n" );
}
// Accept connection
if((new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen))<0){
printf("TCP/IP: Failed to accept incoming connection.\n" );
return -1;
}
printf("TCP/IP: Connection successfully established.\n" );
printf("\n");
fflush(stdout);
// Connection successful. You can send and receive data now.
// Get message from client.
printf("Waiting for message from client...\n");
valread = read(new_socket, buffer, 1024);
printf("FROM CLIENT: %s\n", buffer);
// Pass message to client.
printf("Sending message to client...\n");
char *hello = "serversayshello";
send(new_socket, hello, strlen(hello), 0);
printf("Hello message sent\n");
// Close file descriptors and end program.
close(new_socket);
close(server_fd);
printf("End of program.");
exit(EXIT_SUCCESS);
}
Java客户端
import java.io.*;
import java.net.*;
public class MobileClientPrototype {
public static void main(String[] args) throws IOException{
// Used to get user input.
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Please enter IP Address:");
String host = inFromUser.readLine();
System.out.print("Please enter port number:");
int port = Integer.parseInt(inFromUser.readLine());
// Initialize Socket
Socket clientSocket = new Socket(host, port);
// Streams for communication with server
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
// Ask user for string message which will be sent to server
String sentence;
System.out.print("\nPlease enter message:\n");
sentence = inFromUser.readLine();
// Send message to server
outToServer.writeBytes(sentence + '\n');
System.out.print("Message sent!\n\n");
// Wait for response message from server
String responseSentence;
System.out.print("Awaiting response...\n");
responseSentence = inFromServer.readLine();
// Print response
System.out.println("RESPONSE FROM SERVER:\n" + responseSentence);
// Close socket and end program
System.out.print("\nTerminating connection...");
clientSocket.close();
System.out.print("\nEnd of program.");
}
}
方案
我在本地计算机上运行服务器和客户端程序。使用客户端，我输入127.0.0.1作为服务器打印的IP和端口号。建立连接后，您可以输入将发送到服务器的客户端消息。然后，服务器以 serversayshello 响应。
它适用于一些短字符串，例如，我可以传输 hello ：
但是，如果有一些较长的字符串，客户端会在收到服务器的响应后立即抛出SocketException: Connection reset。
在这里，我正在尝试将 hello从客户端发送到服务器。这就是：
值得注意的是，服务器显然没有收到完整的消息，因为它只打印 hello from 。
错误
Exception in thread "main" java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:210)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
at java.io.InputStreamReader.read(InputStreamReader.java:184)
at java.io.BufferedReader.fill(BufferedReader.java:161)
at java.io.BufferedReader.readLine(BufferedReader.java:324)
at java.io.BufferedReader.readLine(BufferedReader.java:389)
at MobileClientPrototype.main(MobileClientPrototype.java:38)
传输似乎与“hello”，“123456”，“foo”，“bar”，“g g”等短字符串一起使用。
一些不起作用的字符串是： “你好”（大写字母H），“你好客户”，“foobarfoobarfoobar”。
除此之外，我还没有想出一个模式。
什么导致客户端在传输这些较长的邮件时抛出异常？
答案 0 :(得分：0)
您不确定‹���������������HTTP/1.1 200 OK
Host: localhost:8000
Date: Thu, 07 Jun 2018 09:46:54 +0000
Connection: close
Content-Type: application/javascript
Content-Length: 32861
var mr=function(a,b,c){ ... // the rest of js code
是否会在单次调用中返回所有内容（除非您查看已读取的数据的内容或read()的返回值），很多时候它会返回部分数据，您必须再次read()来读取剩余数据
套接字通信的推荐方法是预先确定预期的数据，你可以决定使用固定长度数据并继续调用read()直到总字节数（加上read（）调用的返回值，当大于零表示成功读取的字节数）读取等于您预定的固定长度，或者您可以决定期望新行指示数据结束并继续读取循环直到您收到read()
答案 1 :(得分：0)
“连接重置”有两个常见原因：
还有其他人，但这些是最常见的。两者都是应用程序协议错误。
在你的情况下，线索是它适用于短消息但不适用于长消息，原因是虽然Java代码正在发送由行终止符分隔的消息，但是你只执行一个{{1}在C代码中，并假设这将读取整个消息。在Posix或TCP / IP RFC中无法保证这一点。
如果您期望由行终止符分隔的消息，则必须继续阅读，直到获得它为止。这就是Java的read()方法所做的，而这正是您需要在C代码中模拟的。